Book of Abstracts - CLM

Transcription

COSMO / CLM / ART
User Seminar 2016
Book of Abstracts
Offenbach, March 7 – 9, 2016
Created February 24, 2016 using LATEX and KOMA- Script
Program committee:
For COSMO:
Ulrich Blahak
Deutscher Wetterdienst
Frankfurter Str. 135
63067 Offenbach Germany
Email: [email protected]
For CLM-Community:
Barbara Früh
Frankfurter Str. 135
63067 Offenbach Germany
For COSMO-ART:
Bernhard Vogel
Institut für Meteorologie und Klimaforschung (IMK-TRO)
Karlsruher Institut für Technologie
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen
Germany
Programme
Predictability and Ensemble Systems
1
Soil, Vegetation and Ocean
4
Invited Speaker: Ulrich Schättler
4
Verification (NWP) and Evaluation (RCM)
5
Planetary Boundary Layer
7
NWP Model Applications and Case Studies
9
Invited Speaker: Günther Zängl
11
Dynamics and Numerics
11
Clouds, Chemistry, Aerosol and Radiation
13
Invited Speaker: Angela Benedetti
15
Clouds, Chemistry, Aerosol and Radiation (cont.)
16
Data Assimilation
21
Invited Speaker: Nicole van Lipzig
25
RCM Model Applications
26
Soil, Vegetation and Ocean (cont.)
30
POSTER: Data Assimilation
32
POSTER: Dynamics and Numerics
36
POSTER: Clouds, Chemistry, Aerosol and Radiation
39
POSTER: Soil, Vegetation and Ocean
43
POSTER: Verification (NWP) and Evaluation (RCM)
48
POSTER: Predictability and Ensemble Systems
54
POSTER: NWP Model Applications and Case Studies
56
POSTER: RCM Model Applications
59
1
Regional decadal predictions for Europe in MiKlip
H. Feldmann(1), M. Uhlig(1), Ch. Kottmeier(1)
(1) Institute for Meteorology and Climate Research (IMK-TRO), Karlsruhe Institute of
Technology (KIT), Karlsruhe
Within the last years decadal predictions were an emerging field of research. Its intention is a
better understanding of the natural climate variability and to exploit the predictability derived
from slowly varying components of the climate system on inter-annual to decadal time-scales.
The German MiKlip program aims develop and improve an ensemble prediction system for this
time-scale for later operational use at DWD. MiKlip is organized in modules working on ensemble
generation, model improvement, initialization, relevant processes verification and evaluation and
regionalization.
The prediction system consist consists of the MPI-ESM model for the global scale and a regionalization component based on COSMO-CLM. Dynamical and statistical-dynamical downscaling
methods are applied. Large hindcast experiments for the period 1960 – 2013 were performed to
assess the general skill of the prediction system as well as predictions until 2024. The ensemble
consists of several thousand simulation years, thus providing an excellent data base for ensemble
verification and bias analysis.
The global prediction system is able to achieve a relatively high predictive skill over the North
Atlantic sector. Of special interest is the value added by the regional downscaling. For mean
quantities, like annual mean temperature and precipitation, the predictive skill is comparable
between the global and the downscaled systems, but the regionalization often improves the
reliability. For extremes there seems to be an improvement by the RCM ensemble. The skill
strongly varies on sub-continental regions and with the season. The lead time up to which a
positive predictive skill can be achieved depends on the parameter and season, too. The proper
separation of green-house gas induced trends from the slow modes of natural variability is an
important issue for the decadal predictions, which provides valuable information to the climate
change research community.
2
Performance of dynamically downscaled ensemble seasonal
forecasts over east Africa
S. Asharaf(1), K. Fröhlich(1), J. Fernandez(2), R. M. Cardoso(3), G. Nikulin(4),
B. Früh(1), and the EUPORIAS East Africa Team
(1) Deutscher Wetterdienst, Offenbach, Germany,
(2) University of Cantabria, Santander, Spain,
(3) Rossby Centre, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden,
(4) University of Lisbon, Portugal
Truthful and reliable seasonal rainfall predictions have an important social and economic value
for the east African countries as their economy is highly dependent on rain-fed agriculture and
pastoral systems. Only June to September (JJAS) seasonal rainfall accounts for more than 80 %
crop production in Ethiopia. Hence, seasonal foresting is a challenging concern for the region.
The European Provision of Regional Impact Assessment on a seasonal to decadal timescale
(EUPORIAS) project is a strategic approach to provide improved skill and to address user needs
for seasonal prediction. It offers a common framework to understand model uncertainties through
the use of multi-model and multi-member simulations over east Africa. Under this program, the
participating regional climate models (RCMs) were driven by the atmospheric-only version of
the ECEARTH global climate model, which provides hindcasts of a five-months period (May
to September) from 1991-2012. In this study the RCMs downscaled rainfall is evaluated with
respect to the observed JJAS rainfall, especially over the Ethiopian region. Both deterministic
and probabilistic based forecast skills are assessed. Our preliminary results show the potential
usefulness of multi-model ensemble simulations in forecasting the seasonal rainfall over east
Africa.
Combining Stochastic Pertubation of Physical Tendencies and
parameter perturbation in the COSMO-IT-EPS
convection-permitting ensemble.
Chiara Marsigli(1), Andrea Montani(1), Tiziana Paccagnella(1), Francesca
Marcucci(2), Lucio Torrisi(2)
(1) ARPA Emilia-Romagna SIMC,
(2) COMET
The convection-permitting ensemble COSMO-IT-EPS is entering its pre-operational phase in
2016. The ensemble will be run over Italy at 2.2 km of horizontal resolution, with 10 members.
Aiming at the improvement of the spread/skill relation by revising the perturbation technique
adopted for the COSMO model, the ensemble has been run for one month period in Autumn
2015, starting at 00 UTC of each day and running for 48 hours. Initial and boundary conditions have been provided by the 10-km COSMO-ME-EPS ensemble, developed by the Italian
Air Force Meteorological Centre, which is initialized by a LETKF and which covers the entire
Mediterranean area.
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A pure downscaling ensemble has been compared with a suite where the model physics has
been perturbed by making use of the SPPT scheme implemented in the COSMO model. A third
suite, where SPPT scheme has been combined with perturbed parameters is has also been run,
in order to assess the relative impact of SPPT and parameter perturbation and to study their
complementarity.
Objective evaluation of the forecast quality is performed for 2m temperature and humidity,
against data from the SYNOP network, as well as for precipitation, using high density raingauge
data to allow the application of spatial verification methods in the verification.
TIGGE-LAM ensemble datasets for the prediction of heavy
precipitation events
A Montani, C. Marsigli, T. Paccagnella
ARPA-SIMC, Bologna, Italy
The TIGGE-LAM archive provides a unique opportunity to support research on ensemble
prediction at high spatial resolution. In this contribution, different limited-area model ensemble
prediction systems (LAM-EPSs) from the TIGGE-LAM archive are used to assess the predictability of a number of severe weather events recently occurred over Europe. The added
value of the multi-model with respect to the single-model approach is assessed by investigating the performance of the different LAM-EPSs over a 3-month period and a common overlap
region. The skill of the TIGGE-LAM systems (either running in convection-parameterised or
convection-permitting mode) is mainly studied in terms of probabilistic prediction of precipitation for forecast ranges up to day 5. The relative benefits of higher resolution and/or larger
ensemble size are quantified over the verification period as well as for the individual case studies.
4
A new parameterisation of bare soil evaporation for the land
surface scheme TERRA of the COSMO atmospheric model
Jan-Peter Schulz(1), and Gerd Vogel(2)
(1) Deutscher Wetterdienst, Offenbach am Main, Germany,
(2) Deutscher Wetterdienst, Meteorological Observatory Lindenberg, Germany
Land surface processes have a significant impact on near-surface atmospheric phenomena.
They determine, among others, near-surface sensible and latent heat fluxes and the radiation
budget, and thus influence atmosphere and land characteristics, such as temperature and humidity, the structure of the planetary boundary layer, and even cloud formation processes. It is
therefore important to simulate the land surface processes in atmospheric models as realistically
as possible.
Verifications have shown that the bare soil evaporation computed by the land surface scheme
TERRA of the COSMO atmospheric model is systematically overestimated. Since this flux is
part of the surface water and energy balance it affects, for instance, the other components of
the turbulent heat fluxes as well as the soil water content and the surface temperature.
Data from the Meteorological Observatory Lindenberg of the German Meteorological Service
were used to analyse this model behaviour. In the standard model configuration of TERRA,
the formulation of bare soil evaporation is based on the Biosphere Atmosphere Transfer Scheme
(BATS), following the work by R. E. Dickinson. In order to reduce the excessive evaporation
simulated by BATS, other formulations for the bare soil evaporation were tested in TERRA.
In turned out that a scheme based on a resistance formulation efficiently reduces the simulated
vapour flux, leading to a better agreement with the measurements.
Invited Speaker
New model version COSMO 5.3
Ulrich Schättler
Deutscher Wetterdienst, Offenbach, Germany
Recently a new model version COSMO 5.3 has been released. The talk will give an overview
on the model changes and new features included into this version, as well as an outlook of
developments for the next release.
5
Verification (NWP) and Evaluation
(RCM)
Simulating the Daily Evolution of West African Monsoon using
highresolution Regional COSMO-model: A Case Study of the first
half of 2015 overNigeria
Eniola Olaniyan(1), Ernest Afiesimama(1), Feyi Oni(2)and Kamoru A. Lawal(1).
(1) National Weather Forecasting and Climate Research Centre, Nigerian Meteorological
Agency, Abuja, Nigeria,
(2) Department of Geography, University of Lagos, Lagos, Nigeria
Understanding the dynamics and variability of the West African Monsoon (WAM) at daily
time scales will improve skillful prediction of the onset and evolution of the monsoon and thus
would contribute toward food security of Nigeria. This study, therefore, uses high resolution
regional COSMO-model, a weather-mode model from the German Weather Service adopted
by the Nigerian Meteorological Agency, to study the daily evolution of WAM as well as the
ability of the model to predict the daily characteristics of monsoon, for the first half of 2015,
over Nigeria. Results show that, qualitatively, the model has the ability to predict the daily
evolution of WAM, daily variability of rainfall, which includes the onset of the raining season
as well as dry-spells, over Nigeria. The spatial correlations between the observation and the
forecast are generally greater than 0.64, implying that the model, though, underestimates the
rainfall amount as much as half of the actual amount, it nevertheless proved to have a good
representation of the spatial characteristics of the rain over Nigeria. The model shows that the
Inter-Tropical Discontinuity (ITD) advances northward, from the Gulf of Guinea (GOG) to the
Sahelian region, by about 0.42◦ per week; and that for the onset of monsoon in Nigeria, the
average position of the ITD should be at least 6.7◦ N and must not retreat south of it in the
subsequent average weekly position. In agreement with earlier findings, the model also shows
that the African Easterly Jet (AEJ), together with its associated core, is not only a boreal
summer element but can also exist during the boreal winter with the same strength in the wind
speed. The atmospheric thermodynamic properties, predicted by the model, show that for an
onset of the rains, a threshold value of at least 1500 J K−1 g−1 of convective available potential
energy (CAPE) may be required. The results suggest that COSMO-Model has proved to be a
good tool for operational daily weather forecast; therefore, the model could also have potential
for seasonal rainfall predictions over Nigeria when run in climate mode.
6
A seamless weather-climate multi-model intercomparison on the
representationof a high impact weather event in the Western
Mediterranean: HyMeX IOP12
Samiro Khodayar(1), G. Fosser(2), S. Berthou(3), S. Davolio(4), P. Drobinski(3),
V. Ducrocq(2), R. Ferretti(5), M. Nuret(2), E. Pichelli(5), E. Richard(6),
O. Bock(7)
(1) Institute of Meteorology and Climate Research (IMK-TRO), Karlsruhe Institute of,
Technology (KIT), Karlsruhe, Germany,
(2) CNRM-GAME, CNRS and Météo-France, Toulouse, France,
(3) IPSL/Laboratoire de Météorologie Dynamique, CNRS/UPMC/Ecole Polytechnique,
Palaiseau, France,
(4) Institute of Atmospheric Sciences and Climate (ISAC), National Research Council of Italy
(CNR), Bologna, Italy,
(5) CETEMPS, Department of Physical Science and Chemistry, Universita dell’Aquila,
L’Aquila, Italy,
(6) Laboratoire d’Aérologie, Université de Toulouse/CNRS 5560, Toulouse, France,
(7) IGN LAREG, Univ Paris Diderot, Sorbonne Paris Cité, 75013 Paris, France
High Impact Weather (HIW), particularly Heavy Precipitation Events (HPE), are common
phenomena affecting the Western Mediterranean (WMED) especially in the fall period. Understanding and evaluating the capability to adequately represent such events in model simulations
is one of the main goals of the Hydrological cycle in the Mediterranean Experiment (HyMeX)
and the main motivation of this investigation.
In order to gain a better knowledge of the model representation of HPE and related processes
we perform a seamless multi-model intercomparison at the event scale. Limited area model
runs (grid spacing from 2 to 20 km) at weather and climate timescales are considered, four with
parameterized and five with explicit convection. The performance of the nine models is compared
by analysing precipitation, as well as convection-relevant parameters. An Intensive Observation
Period (IOP12) from the HyMeX-SOP1 (Special Observation Period) is used to illustrate the
results. During IOP12, HPE affected the north-western Mediterranean region, from Spain to
Italy, as a consequence of Mesoscale Convective Systems (MCSs) which initiated and intensified
in the area of investigation.
Results show that: (i) the timing of the maximum precipitation seems to be linked with the
representation of large-scale conditions rather than differences among models, (ii) Convection
Permitting Models (CPMs) exhibit differences among each other, but better represent the shortintense convective events. All four convection-parameterised models produce a large number
of weak and long-lasting events. Regional Climate Models (RCMs) capture the occurrence of
the event but produce notably lower precipitation amount and hourly intensities than CPMs
and Numerical Weather Prediction (NWP) models with parameterized convection. (iii) These
differences do not seem to come from mean moisture or Convective Available Potential Energy
(CAPE) which are in the same range for all models, but rather from differences in the variability
and vertical distribution of moisture and the triggering of deep convection.
7
Meteodrones - revealing the unknown of the boundary layer
Martin Fengler, Nils Dorband
Meteomatics
The Planetary Boundary Layer (PBL) is the main trigger of phenomena like fog, low stratus,
freezing rain and thunderstorms. For a lack of measurements in this layer however, forecasts of
existing weather models often are not as accurate as desired. Therefore, in 2012 Meteomatics
started a drone measurement campaign and finally conducted 450 sounding flights in the first
two weeks of July 2015. In five locations (Altenrhein, Amlikon, Bad Ragaz, Oberriet and Schänis) highly accurate measurements of weather parameters in the boundary layer up to 1.5 km
above ground were performed and are now being analysed. However, it is already clear that the
Meteodrones revealed weather phenomena, which have been unknown until today. For example,
due to the Meteodrone data the in- and outflow of the Rhine valley became evident. Thus,
the meteodrones help to improve short-term forecasts and to reach the self-imposed target of
creating the perfect 24-hour forecast.
Diagnostics and Revision of the COSMO Surface Layer
Formulation under StableConditions
I. Cerenzia (1, 2), M. Raschendorfer(3)
(1) University of Bologna, Italy,
(2) Arpa-SIMC Emilia Romagna, Bologna, Italy,
(3) Deutscher Wetterdienst, Offenbach am Main, Germany
COSMO model applies a transfer scheme based on the decomposition of the surface layer in
sub-layers, treated in terms of aerodynamic resistances. Specific assumptions and interpolations
are used to calculate the sub-layers transfer resistances, while information about the turbulence
state are inferred from the turbulence scheme, adapted from Mellor and Yamada (1982).
In the framework of COSMO PP ConSAT a different interpolation formula of the surface layer
profile function has been tested against the previous formulation, as well as against an empirical
and a semi - empirical scheme based on Monin-Obukhov similarity theory in the framework of
a simplified single column version of COSMO model, by focusing on homogeneous terrain and
stable stratification.
Results indicate that the previous formulation defects in reproducing the transfer drop at
high stability, largely overpredicting in absolute value the observed surface fluxes. However,
the consequent improvements are visible only by reducing some of the turbulent - enhancing
measures, currently still necessary to keep high the operational large scale scores.
8
New features of the common turbulence parameterization for
COSMO and ICON
Matthias Raschendorfer
Recently the unified module TURBDIFF has been implemented into COSMO model, containing the closure model for atmospheric turbulence (including a related statistical saturation
adjustment and the calculation of turbulent diffusion), as well as its application in order to
describe surface-to-atmosphere-transfer (SAT). By this, COSMO and ICON share one and the
same turbulence module, which has been extended first of all by some modifications in the course
of adapting the contained schemes for their application in the new global model ICON. Other
extensions have been introduced in order to successively reduce existing restrictions for stable
stratification.
All the extensions can be (de-)activated by parameter settings in a configuration module, and
most of them are already active in ICON. In this talk, some of these extensions are explained,
which also are a matter in two of the following presentations. One special extension being
explained is a correction of the SAT scheme for stable stratification (by introducing a hyperbolic
interpolation for the vertical transfer layer profile of turbulent velocity scale), which is not yet
active in any operational configuration. It was developed some years ago and has already been
implemented into the common module during the ConSAT task. Some first results and a deeper
diagnostic based on surface-flux measurements are being presented in the subsequent talk.
EWeLiNE and ORKA- optimizing the turbulence parametrization
for Renewable Energies
J.v.Schumann, A.Steiner, C.Koehler
In 2014, wind and solar power produced 16.4 % of the country’s net public energy supply (ISE,
2014). To safely integrate the increasing share of renewable energies, accurate power predictions
are necessary. These, in turn, depend on high quality Numerical Weather Prediction (NWP)
models. Within the two projects EWeLiNE and ORKA, the aim is to improve the COSMO-DE
model with respect to wind speed forecasts in hub heights and radiation forecasts.
Currently, a unified physics package for the use in ICON as well as in COSMO is in preparation.
With regard to Renewable Energy applications, the turbulence model is of special importance.
Therefore, we investigate which innovations and optimized settings concerning the turbulent
diffusion can be used in the COSMO-DE configuration. Special focus is laid on stable nights
with the development of Low Level Jets and high pressure situations with low stratus formation.
ISE, 2014: https://www.ise.fraunhofer.de/de/downloads/pdf-files/data-nivc-/stromproduktionaus-solar-und-windenergie-2014.pdf
9
NWP Model Applications and Case
Studies
Model Application and Validation of a new Parameterization
Framework for Heterogeneous Ice Nucleation on Desert Dust and
Soot
R. Ullrich(1), C. Hoose(1), O. Möhler(1), D. Cziczo(2), K. Froyd(3), B. Vogel(1),
H. Vogel(1), T. Schad(1), D. Rieger(1), K. Deetz(1)
(1) Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research,
Karlsruhe, Germany,
(2) Massachusetts Institute of Technology, Earth, Atmospheric and Planetary Science,
Cambridge/ MA, U.S.,
(3) NOAA, Earth System Research Laboratory – Chemical Science Division, Boulder/ CO,
U.S.
Ice particles in the atmosphere are important for cloud lifetime, precipitation or radiation.
In mixed- phase clouds as well in cirrus clouds, aerosols contribute to the formation of ice
particles. However, a uniform handling of the aerosols ice nucleation ability and efficiency is not
possible and therefore, a variety of parameterization schemes therefore exists. Studies comparing
different parameterization for heterogeneous ice nucleation in models show a high variability in
the resulting ice water path values and their spatial distribution (e.g. Komurcu et al. (2014)).
A newly developed parameterization framework for heterogeneous ice nucleation of desert dust
and soot based on 11 years of AIDA cloud chamber experiments (Ullrich et al. in prep.) was
implemented into the online- coupled model COSMO-ART (Vogel et al. (2009)).
The aim of this study is to compare the modelling results using the new parameterization
scheme (Ullrich et al. in prep.) and the standard parameterization scheme of Phillips et al.
(2008) and to compare the modelling results with in-situ measurements.
This contribution will show the results for a case study on a synoptically driven cirrus cloud
over the south central U.S. Here, especially the contribution of desert dust and black carbon
particles to the total number of heterogeneously formed ice particles will be compared and be
checked against ice residuals measured during the MACPEX campaign in April 2011 (Cziczo et
al. (2013)).
Furthermore, the study will show the use of ICON-ART dust emission model output for
initializing the COSMO-ART dust load.
10
Nested Data Assimilation with KENDA for COSMO-MUC
Heiner Lange(1), Tijana Janjic(2)
(1) Hans-Ertel-Centre for Weather Research, Data Assimilation Branch, LMU Munich
(2) , Hans-Ertel-Centre for Weather Research, Data Assimilation Branch, Deutscher
Wetterdienst, Offenbach
COSMO-MUC is being developed by Ingo Soelch (DLR) as a testmodel for very short-range
forecasts at the Munich airport MUC with a frequent nudging analysis cycling. It has a horizontal
resolution of 1.4 km and a domain-extent of 300 by 300 km centered around MUC.
COSMO-MUC-KENDA (Kilometre-scale ENsemble Data Assimilation) is being developed
in parallel as a nested version of the pre-operational KENDA of COSMO-DE. The ensemble
data assimilation of MUC-KENDA uses analyses and forecasts of 40+1 hourly cycled ensemble
members of COSMO-DE as boundary conditions for the 40+1 members of the COSMO-MUC
ensemble. For MUC-KENDA, data assimilation parameters are varied, such as the horizontal
localization length of observation influence or the analysis cycling interval which is reduced from
60 to 15 minutes.
With the assimilation of conventional observations such as surface and aircraft data of AMDAR and Mode-S, the quality of analyses and 3-hour forecasts starting from simultaneous analyses is comparable for preliminary setups of COSMO-MUC and COSMO-DE. By adding convective scale observations such as radar reflectivity and radial velocity, it is tested whether
the different representation of deep convection due to the higher resolution of COSMO-MUC
causes differences or improvements with respect to COSMO-DE, for example in quantitative
precipitation forecasts.
New operational applications at Meteoswiss on hybrid
supercomputer
O. Fuhrer(1), M. Arpagaus(1), A. Walser(1), D. Leuenberger(1), G. deMorsier(1),
X. Lapillonne(1), P. Spoerri(2), and the COSMO-GPU team
(1) Meteoswiss,
(2) ETH Zürich
A new set of operational applications, COSMO-1 (1km resolution), COSMO-E (ensemble)
and KENDA (assimilation) are being introduced at MeteoSwiss as part of the COSMO-next
project. The new applications requires an increase of a factor 40x in terms of computational
power as compared to the current operational setup. This was made possible by the use of the
new GPU-version of the COSMO model which was developed in parallel to the project together
with a the acquisition of a dedicated hybrid supercomputer.
This talk will first present results and status of the new operational applications. An overview
of the porting approach of the COSMO model to GPUs is then provided together with performance results on the new hybrid Cray CS-Storm computer, Piz Kesch.
11
Invited Speaker
ICON: Status after one year of operational NWP and further
plans
Günther Zängl
Deutscher Wetterdienst, Germany
The ICON (ICOsahedral Nonhydrostatic) model became the operational global numerical
weather prediction system at DWD on January 20, 2015, replacing its predecessor GME after
about 15 years of operational usage. The global ICON grid has a horizontal mesh size of about
13 km and 90 vertical levels with a top at 75 km. Half a year later, on July 21, 2015, a twoway nested domain over Europe was activated, having a mesh size of 6.5 km and 60 levels
up to 22.5 km. This refined domain, internally called ICON-EU, will soon replace the current
COSMO-EU running at a mesh size of 7 km. The next major upgrade of DWD’s global and
regional weather forecasting system, namely the hybrid Ensemble-Kalman-Filter / 3D-Var data
assimilation system (EnVar), was put into operations on January 20, 2016.
The presentation starts with a brief description of the main components of the ICON modelling system, followed by an overview of the improvements in forecast quality with respect to
GME and COSMO-EU. Afterwards, the status of the limited-area mode of ICON will be presented, including results of first case studies and perspectives for future applications in NWP
and research.
3D diffusion in steep terrain: testing and stability of horizontally
explicit, vertically implicit discretizations
M. Baldauf
Turbulent diffusion is an important process not only in the atmospheric boundary layer, but
also partially in the troposphere and e.g. due to gravity wave breaking even in higher parts of
the atmosphere. From a numerical viewpoint, stability of the diffusion operator may be limited
in terrain-following coordinate systems if the HE-VI (horizontally explicit-vertically implicit)
approach is applied. The latter is often used in global and regional atmospheric models. The
problem may arise due to the metric correction terms in steep terrain, when they are treated
explicitly.
The aim of the presentation is twofold. Firstly, a spatially second order discretization is proposed which treats the metric terms of the terrain following coordinates in a stable manner even
12
for steep terrain. A von-Neumann stability analysis calculates the maximum stable diffusion
Courant number for different implicitness weights both for scalar diffusion and for vector diffusion (i.e. for the momentum equation). In the scalar case even an exact stability condition may
be given.
Secondly, simple exact analytic solutions of the diffusion equation for both the scalar and the
vector case are proposed for testing and validation purposes. Such tests are very helpful since
the diffusion equations have a quite complicated structure in terrain following coordinates on
the sphere. These tests can also be used for diffusion on ’small planet’ simulations.
New dynamical core of COSMO –“COSMO-EULAG
operationalization (CELO)” priority project
Z.P. Piotrowski, B. Rosa, D.K. Wojcik
Institute of Meteorology and Water Management - National Research Institute
CELO priority project was accepted at the COSMO General Meeting 2012 and aims to implement and integrate the compressible EULAG dynamical core with the operational COSMO
model to allow for operational high-resolution forecast. Here we report on the progress of the
project in the areas of: dynamical core development, integration of the compressible core with
COSMO framework, verification and computational performance.
13
Physical subgrid information exchange between parameterization
schemes in COSMO
V. Kuell, A. Bott
Meteorological Institute, University of Bonn
Numerical weather prediction (NWP) models have to solve the basic differential equations
in a spatially and temporally discretized form. By introducing a numerical grid, all processes
of subgrid scales are cut off and have to be parameterized to close the system of prognostic
equations and to include their influence on the grid scale averages. In fact, the behavior of the
NWP model is crucially influenced by the choice of physical parameterizations.
Contemporary physical parameterization schemes calculate detailed information
of the processes in question, but they only provide a fraction of this information as tendencies
of the prognostic variables to the grid scale. Subgrid scale information is usually not directly
communicated between the different parameterization schemes. The only way for this communication is via the
averaged model variables. This causes a significant loss of information due to the grid scale
averaging and the restriction to the chosen set of prognostic variables.
To overcome this loss of information we introduce a physical subgrid scale information exchange (PSIE) between the parameterization schemes. We will demonstrate the effect of selected
parameters which are directly passed among the parameterization schemes. Real case simulations employing the COSMO model of DWD with and without our PSIE system will be analyzed
and compared to observations.
Clouds, Chemistry, Aerosol and
Radiation
Modeling the melting of graupel and hail in a bulk
microphysicsparameterization
Vivek Sant(1)and Axel Seifert(2)
(1) Max Planck Institute for Meteorology,
(2) Deutscher Wetterdienst
The melting rates of graupel and hail are decisive for the amount of ice reaching the ground,
but the melting processes can also strongly affect the dynamics of convective and even frontal
systems due to the associated cooling of the air. For comparison of high-resolution simulations
with remote-sensing observations like radar an explicit prediction of the melting of graupel and
hail allows for a more accurate treatment in the forward model, i.e. the calculation of radar
reflectivities from model variables. To develop an advanced melting scheme the fundamental
properties of melting graupel and hail are revisited and parameterization are compiled based
14
on available laboratory measurements of individual particles. Using those empirical relations
in a spectral, i.e. size-resolved, 1D iceshaft model lays the foundation on which the new bulk
model is derived. To arrive at a bulk parameterization several simplifications are necessary. For
example, we show that for a melting hail particle the internal conduction term, which in general
depends on the actual temperature gradient between the engulfed ice core and the liquid surface,
can be replaced by a simpler correction term considering only the thickness of the liquid layer.
Shedding of melt water is a secondary process that occurs during melting and affects the fall
velocity of the melting particle and also the melting rate itself. It is shown that a physically-based
parameterization of shedding in a two-moment bulk scheme is possible, but large uncertainties
remain due to the complexity of the microphysical behavior of melting graupel and hail. Based
on this study we suggest a new parameterization of the melting processes of graupel and hail for
use in two-moment bulk schemes, which has the important advantage that the amount of liquid
water on melting graupel and hail is explicitly predicted.
Priority Project T2(RC)2 – an overview
H. Muskatel(1), P. Khain(1), U. Blahak(2)and A. Shtivelman
(1) Israeli Meteorological Service,
The main goal in the T2(RC)2 project is to improve the model’s cloud-radiation-coupling. We
intend to test the (RC)2 PT results of the new optical properties of clouds and will continue to
explore the model sensitivities to several new tuning parameters. The second goal is to improve
the aerosols input to the radiation scheme using new available data such as the prognostic
aerosols fields of the CAMS-ECMWF and the Kinne aerosol climatology. We will also re-examine
the current Sub-Grid scale clouds scheme used in the radiation code.
Some numerical aspects of the radiation code will be addressed, such as the temporal resolution
optimization, the "Monte-Carlo Spectral Integration" (MCSI) and the transformation of the
radiation code into single precision.
Experimental datasets from Moscow State University Meteorological Observatory will be used
for testing both the radiation code and new aerosol inputs. Testing the sensitivity of main
prognostic meteorological characteristics to the changes in radiation fields and the assessment
of the forecast quality to the changes made in radiation scheme with the different aerosol/cloud
inputs will be also fulfilled.
15
Priority Project T2RC2 : Determination of governing parameters
in the new radiation scheme
Pavel Khain(1), Harel Muskatel(1)and Uli Blahak(2)
(1) Israeli Meteorological Service (IMS),
(2) Deutscher Wetterdienst (DWD)
Priority Project “Testing and Tuning of Revised Cloud Radiation Coupling” (T2RC2) aims to
finalize several years of work (by U. Blahak et al.) in developing the new cloud-radiation coupling
scheme in the COSMO model. The new scheme takes into account many new cloud-radiation
interaction processes yielding twenty five continuous parameters and seven logical switches. Part
of these parameters (and switches) are of high influence on the radiation in the model while others
are of lower importance.
The idealized COSMO framework is used to determine the model radiation sensitivity to parameters for different cloudiness conditions, including fair weather cumulus, low stratocumulus,
low stratus, mixed (ice/water) phase cloud, cirrus, and anvil of cumulonimbus.
We present the method used to determine model radiation sensitivity to the new parameters.
We define the most sensible parameters (and switches) which will be part of the Namelist in a
future COSMO release, while the others will be predefined within the code. A short physical
description of the main parameters which will enter the Namelist is also presented.
Invited Speaker
Aerosol modelling and assimilation at the European Centre for
Medium-Range Weather Forecast
Angela Benedetti
European Centre for Medium-Range Weather Forecasts
Aerosol modelling and assimilation has become an important activity at many forecasting centres around the world. At the European Centre for Medium-Range Weather Forecast (ECMWF)
the numerical weather prediction model has been modified to allow the prediction of atmospheric
composition fields as well as their impact on the weather, thanks to several EU-funded projects
(GEMS, MACC, etc). Currently ECMWF manages the Copernicus Atmosphere Monitoring Service (CAMS) which provides a large portfolio of products related to aerosols, reactive gases and
greenhouse gases. These products include regional air-quality forecasts as well as global reanalyses for climate monitoring which are freely made available to the public. In this talk we will
present the general model and assimilation architecture, with focus on the aerosol component,
and give an overview of the available products. Some examples of NWP-specific applications
will be also provided.
16
Clouds, Chemistry, Aerosol and
Radiation (cont.)
The accuracy assessment of the COSMO-Ru radiative
calculations using different aerosol climatologies and their
influence on temperature forecast
N. Ye. Chubarova (1, 2), A.A. Poliukhov (1, 2), G.S.Rivin (1, 2),
M.V.Shatunova(2)
(1) Lomonosov Moscow State University, Faculty of Geography, Moscow, Russia,
(2) Hydrometeorological Centre of Russia, Moscow, Russia
The results of COSMO-Ru radiative simulations were tested against ground-based radiative
measurements and model data in clear sky conditions with different aerosol properties, water
vapor content and surface albedo. For this purpose we applied the data of Meteorological Observatory of Moscow State University, which include the input parameters necessary for modeling
(aerosol and water vapor datasets from CIMEL AERONET sun photometer), and different
shortwave and longwave radiation component datasets from CNR-4 Kipp&Zonen net radiometer measurements. Accurate radiative simulations were performed by Monte-Carlo RT model [3]
and the modified CLIRAD-SW code [5].
Using this composite approach we tested both the COSMO radiation algorithm developed
in [2] and the effects of aerosols applied in COSMO-Ru model. In addition to standard aerosol
climatologies, the new MACv2 aerosol climatology was also used [1]. We show that both Tanre
and Tegen aerosol climatologies [4,6] provide much higher aerosol loading compared with real
aerosol conditions in Moscow, that results in large biases in the calculation of the downward
shortwave radiation.
The application of various aerosols in COSMO RT codes has led to a pronounced temperature
effect. We showed that in clear sky conditions the sensitivity of temperature at 2m is about
0.7-1.1 degrees C per 100 W/m2 in shortwave net radiation change due to aerosol variations.
We also tested the effects of different aerosols on the quality of temperature forecast.
References:
1. Kinne, S., O’Donnel D., Stier P., et al., J. Adv. Model. Earth Syst., 5, 704–740, 2013.
2. Ritter, B. and Geleyn, J., Monthly Weather Review, 120, 303-325, 1992.
3. Rublev, A., Trotsenko A., Trembach V., and Kopylov A., A. Deepak Publ., Hampton,
Virginia, 1105-1108, 2001.
4. Tanre, D., Geleyn, J., and Slingo, J., A. Deepak Publ., Hampton, Virginia, 133-177, 1984.
5. Tarasova, T., and Fomin, B., Journal of Atmospheric and Oceanic Technology, 24, 11571162, 2007.
6. Tegen, I., Hollrig, P., Chin, M., et al., Journal of Geophysical Research - Atmospheres, 102,
23895-23915, 1997.
17
Simulating aerosol-cloud interactions in southern West Africa
with COSMO-ART in the framework of DACCIWA
Konrad Deetz, Bernhard Vogel
Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT)
The Dynamics-aerosol-chemistry-cloud interactions in West Africa (DACCIWA) project investigates the influence of anthropogenic and natural emissions on the atmospheric composition
over southern West Africa (SWA). By using the regional scale comprehensive model system
COSMO-ART (Vogel et al., 2009) we quantify the influence of the atmospheric composition
on radiative forcing, the two-way coupling between aerosols and cloud droplets as well as
precipitation and shed light on the characteristics of cloud microphysics and dynamics in SWA.
A double nesting from 28 km grid mesh size (including Saharan mineral dust from the north
and biomass burning emissions from southeast) to 3 km over the research area was realized.
For the finest mesh size, we use explicit convection and consider aerosol-cloud interactions
(ACI). A special interest we have in the influence of aerosols on the nocturnal low-level stratus
(NLLS). The NLLS frequently occurs in extended areas over SWA with a cloud base height
of 200-400 m, forming at night and persisting into the early afternoon hours (Schuster et al.,
2013). A COSMO-ART case study simulation for June 7-8, 2014 shows remarkable changes in
the simulated vertical resolved cloud cover and specific cloud liquid water content when using
ACI. An increased extension and a reduced cloud base (relatively homogeneous at approx. 300
m) over Togo and Benin can be observed in comparison to the simulation without ACI. This
leads to positive anomalies of cloud liquid water up to 0.5 g kg-1. In addition to the objectives
mentioned above, numerical forecasts with COSMO-ART for the DACCIWA measurement
campaign in June/July 2016 will be performed, supporting the decision-making of the flight
routes for the research aircrafts. The German Weather Service (DWD) provides ICON forecasts
for the meteorological boundary conditions. The presentation will show selected results of
pre-operational forecasts.
Vogel, B., Vogel, H., Bäumer, D., Bangert, M., Lundgren, K., Rinke, R., Stanelle, T., 2009:
The comprehensive model system COSMO-ART - Radiative impact of aerosol on the state of
the atmosphere on the regional scale, Atmos. Chem. Phys., 9, 8661-8680.
Schuster, R., Fink, A. H., Knippertz, P., 2013: Formation and Maintenance of Nocturnal LowLevel Stratus over the Southern West African Monsoon Region during AMMA 2006, Journal of
the Atmospheric Sciences, Vol. 70, 2337-2355.
18
Simulating Contrails on the Regional Scale to Predict Energy
Yield of Photovoltaic Systems
S. Gruber(1), J. Bechtold(2), B. Vogel(1), H. Vogel(1), M. Jung(2), H. Pak(2)
(1) Institute of Meteorology and Climate Research, KIT, Germany,
(2) Institute of Air Transport and Airport Research, DLR, Cologne, Germany
Condensation trails (contrails) from aircrafts are among the most obvious indications showing
anthropogenic activities impacting the atmosphere.
To study this phenomenon, the high resolving regional numerical model system COSMOART (Baldauf et al., 2011; Vogel et al., 2009) was extended by a parameterization that allows
calculating both the generation as well as the life cycle of contrails.
Based on the Schmidt-Appleman-Criterion (Schumann, 1996), the parameterization provides
source terms for contrail ice. The following life cycle that consists of processes like deposition
of water vapor, sedimentation sublimation and collection processes is described using a two
moment cloud microphysical scheme of Seifert and Beheng (2001). For a better representation
of the small crystals occurring in contrails, a separate contrail ice class was introduced here.
This extended model system is capable of simulating so-called contrail cirrus that give name
to aged contrails which more and more develop into wide spread and optical thin cirrus.
The additional cirrus modifies the radiative budget of the atmosphere. To quantify this effect,
the radiation scheme was changed in way to fulfill the requests that go along with the very small
ice particles in contrails. To our knowledge, the present study with such a configuration is the
first one of its kind.
A basic data set provided by the German Aerospace Center - Institute of Air Transport and
Airport Research (DLR) contains the spatial and temporal high resolved trajectories of a limited
number of sample flights over Central Europe derived by real time data.
A case study was performed proofing that considering contrails and contrail cirrus strongly
improves the reproduction of satellite based observations. The main emphasis of this study is
put on examining the influence on the radiative budget at the earth’s surface regarding gain
or loss of energy yield of photovoltaic systems due to contrails and contrail cirrus. Next to a
slightly positive contribution in the thermal spectrum, the shading effect is dominant, especially
for short-wave radiation, causing losses up to 10 %.
19
Sensitivity study about the dissipation of an Arctic mixed-phase
cloud during the ASCOS field campaign
Katharina Weixler(1), Annica Ekman(2), Corinna Hoose(1), Marco Paukert(1),
Joseph Sedlar(2), Michael Tjernström(2)
(1) Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology,
Karlsruhe, Germany,
(2) Department of Meteorology, Stockholm University, Stockholm, Sweden
Mixed-phase clouds are important for the surface energy budget in the Arctic. They can
absorb long wave radiation from the surface and also reflect solar radiation back to space,
which can lead to either cooling or warming of the lower atmosphere. The Arctic climate is
changing and these changing conditons affect the Arctic boundary layer and the Arctic mixedphase clouds. Mixed-phase clouds contain supercooled liquid water and ice at the same time.
Furthermore, this mixture of liquid droplets and ice is unstable, which influences the lifetime
of such a cloud. Different field campaigns help to understand and improve the simulation of
Arctic mixed-phase clouds and their impact on climate. This study focus on the ASCOS (Arctic
Summer Arctic Cloud Ocean Study) campaign. The ASCOS field campaign took place in 2008.
It was an extensive in-situ field experiment and lasted for more than one month (Tjernström
et al., 2012). The icebreaker Oden was mored for 3 weeks on an ice-drift near 87◦ N. Long term
studies of the Arctic ocean and atmosphere were done during mid of August through beginning of
September. These long term measurements allow a great look at cloud development in the Arctic.
With the COSMO (Consortium for Small-scale Modelling) model a sensitivity study of the
dissipation processes of one Arctic mixed-phase cloud during ASCOS is conducted. The doublemoment cloud microphysics scheme is used in a semi-idealized LES (Large Eddy Simulation)
setup, which has a horizontal resolution of 100 m and periodic boundary conditions. Possible
dissipation processes such as dry-air advection above the cloud, reduced CDNC and enhanced
IN concentration are analyzed with a closer look at the boundary layer structure and the cloud
microphysics.
Idealized large-eddy 100m resolution COSMO simulations of
selected boundary-layermixed-phase clouds with observational
data from the RACEPAC campaign
J. Hesemann(1), C. Hoose(1), K. Weixler(1), J. Fugal (2, 3), M. Klingebiel(2), S.
Borrmann (2, 3), A. Ehrlich(4), M. Maturilli(5)
(1) Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology,
Karlsruhe, Germany,
(2) Institute for Physics of the Atmosphere, University of Mainz, Mainz, Germany,
(3) Max Planck Institute for Chemistry, Mainz, Germany,
(4) Leipzig Institute for Meteorology (LIM), University of Leipzig, Leipzig, Germany,
(5) Alfred Wegener Institute for Marine and Polar Research, Bremerhaven & Potsdam,
Germany
Arctic mixed-phase clouds play an important role in understanding climate change.
20
We present idealized large-eddy 100 meter resolution COSMO simulations initialized with
observational data of selected flights from airborne measurements, conducted 2014 during the
Radiation-Aerosol-Cloud Experiment in the Arctic Circle (RACEPAC) campaign. Emphasis is
put on cloud-near-surface-layer interaction. In RACEPAC
flight No. 1, dropsonde vertical profiles and cloud microphysics data were available at similar
cloud conditions in the same region above water and sea ice. Yet, wind speed in the z 0-1 km layer
above water was observed to be significantly lower despite the smoother surface. We reproduced
this behaviour in model set-ups for a water and ice covered case and present how mixing layer
and cloud properties are affected by the water/ice surface.
Ice nucleation in semi-idealised, high resolution simulations
Luke B. Hande, Corinna Hoose
Karlsruhe Institute of Technology
Ice microphysical processes have a large influence on cloud radiative properties, lifetime, and
precipitation amounts. Therefore understanding the dominant processes through which ice forms
is important on all spatial and temporal scales. Here, the COSMO model is run at very high
resolutions of 100m, which is capable of resolving energy containing turbulence. A number of
semi-idealised case studies are preformed with state of the art parameterisations for contact
nucleation, immersion freezing, and deposition nucleation. Results will be presented for a semiideal case of a convective cloud, which indicate immersion freezing is the dominant pathway
through which ice forms. Contact nucleation plays an important role at warmer temperatures,
and deposition freezing contributes only a small amount to the total INP concentrations.
Data Assimilation
21
A case study of particle accumulation in rain drops and
immersion freezing
M. Paukert(1), C. Hoose(2)
(1) IMK-AAF, KIT,
(2) IMK-TRO, KIT
A common assumption in aerosol-dependent freezing parameterizations is that each particle
corresponds to exactly one cloud droplet. In contrast, the immersion freezing of rain is usually
represented by a liquid volume-dependent approach following Bigg (1953), making the process
of rain freezing independent of specific aerosol types and concentrations. This may lead to
inconsistencies when aerosol effects on clouds and precipitation are the subject of interest, since
rain drops consist of the cloud droplets (and corresponding aerosol particles) that have been
involved in drop-drop-collisions.
To make rain immersion freezing sensitive to aerosols, we extended COSMO’s two-moment
microphysics (Seifert and Beheng, 2006) to explicitly account for particle accumulation in rain
drops by tracking the rates of selfcollection, autoconversion and accretion. Accordingly, also
the primary formation of graupel and hail particles is directly influenced by ice nuclei (Blahak,
2008).
In our test cases of idealized deep convective clouds (Weisman and Klemp, 1982) we find
that at altitudes which are most relevant for freezing, very most of the potential ice nuclei have
been converted from cloud droplets into rain drops. The less efficient freezing of mineral dust
(Niemand et al., 2012) compared to the Bigg approach results in higher rain water contents
in the convective core and enhanced surface precipitation of both rain and hail. In our studies
with focus on the influence of ice nuclei concentrations on cloud property changes, the extended
treatment of rain freezing exhibits the potential to reverse the signs of several sensitivities.
Data Assimilation
Towards an operational use of the KENDA system at DWD
Christoph Schraff, Hendrik Reich, Andreas Rhodin, Roland Potthast, Klaus
Stephan
DWD, Offenbach, Germany
A Local Ensemble Transform Kalman Filter (LETKF) data assimilation for convectionpermitting NWP has been developed in the framework of a COSMO Priority Project called
KENDA (Km-scale ENsemble-based Data Assimilation). We will present the current status of
the developments for the ‘KENDA system’ and recent results from tests carried out towards
its operational use at DWD. In these tests, the KENDA system was compared to the current
operational data assimilation scheme based on observation nudging. Both schemes used the basic
conventional observation types that are currently assimilated operationally, and are combined
22
Data Assimilation
with latent heat nudging for the assimilation of radar-derived precipitation rates. Our presentation of the status of KENDA will also include a brief overview of further work and projects
dealing with the use of additional, high-resolution observation data in KENDA.
Assimilation cycle in observation-sparse regions
Pavel Khain, Alon Shtivelman, Anat Baharad, Harel Muskatel and Yoav Levi
Israeli Meteorological Service
When initializing a regional model (RM) forecast, generally two options exist: either performing a “cold start”, i.e. interpolating coarse grid analysis to the RM fine grid, or a “warm
start”, i.e. utilizing a forecast of a previous RM run performed with continuous data assimilation
(nudging). The latter option yields a continuous “assimilation cycle” of RM, removing spin-ups
and allowing RM to develop its “own model climate”. In case the assimilation cycle is applied,
the forecasts are constrained only by the boundary conditions and the observations within the
model domain. “Assimilation cycle” is widely used by National Weather Services and is generally
being preferred over the “cold starts” option.
The problem arises when observations density within the RM domain is low, as occurs for
example in the Eastern Mediterranean. In that case, “assimilation cycle” runs are not constrained
with enough observations, and the forecasts may diverge from real weather. A common method
to tackle this problem is to interfere the “assimilation cycle” by a “cold start” from time to time.
However, this method is highly problematic, as the optimal time for a continuous “assimilation
cycle” varies according the synoptic conditions.
A possible solution was proposed recently at the Israel Meteorological Service (IMS). At
the beginning of every forecast cycle, it is proposed to perform a “quick” verification of the two
analysis files (“cold start” and “warm start”) against the observations available at the initialization
time. The “better” analysis should be chosen as the initial conditions for the next cycle of the
model forecast.
We will show that utilization of the proposed method leads to the improvement of the COSMO
forecasts over the Eastern Mediterranean, in comparison with the continuous “assimilation cycle”.
The proposed performance score for analysis verification is also discussed.
Data Assimilation
23
Impact of radar reflectivity assimilation in KENDA: the Italian
experiment
Virginia Poli, Chiara Marsigli, Tiziana Paccagnella, Pier Paolo Alberoni
ARPA Emilia-Romagna
To allow the assimilation of reflectivity from the italian radar network into the Kilometerscale ENsemble Data Assimilation (KENDA) LETKF system the ODIM HDF5 reader has been
implemented into the COSMO Radar Forward Operator (EMVORADO). Even if, so far, the
system has been applied only to assimilate some of the italian radars, the reader permits the
ingestion of all of the radar data coded in HDF5 according to OPERA data information model
(ODIM HDF5), and can be used by all the COSMO users.
The final aim of our project is the assimilation of the reflectivity volumes of the whole italian
radar network, managed by different institutions but centralized by the National Department of
Civil Protection. Preliminary tests were accomplished to take into account the great heterogeneity of scanning modes coming from this distributed management. The problem of a homogeneous
quality definition will be tackled in the next step of this work.
The experimental framework is a continuous assimilation cycle implemented with a 3-hourly
step, with Boundary Conditions (and Initial Conditions for the cold start) from 20 members of
the ECMWF ensemble. In this work it is shown the impact of the assimilation of Pettinascura
radar, during a flood event which took place over the Calabria Region. For this case the impact
of different configurations of superobbing and data thinning, as well as the temporal resolution of
the volumes is analysed, taking into account also the issues of computational time and required
resources.
Pre-operational, convective-scale Ensemble Data Assimilation at
MeteoSwiss
Daniel Leuenberger, Simon Foerster, Andre Walser
MeteoSwiss
MeteoSwiss currently tests a new COSMO prediction system consisting of a 1km deterministic (COSMO-1) and a 2km ensemble (COSMO-E) configuration in pre-operational mode. Initial
condition perturbations for the ensemble forecasts are provided by a Local Ensemble Transform Kalman Filter (LETKF) method. This contribution presents results of the Swiss COSMOLETKF system for different periods. The quality of the analyses will be investigated, and the
deterministic analysis will be compared against a standard nudging analysis.
At a later stage, the LETKF system will also provide deterministic initial conditions for
the COSMO-1 forecasts. We will present first results of forecasts initialized by the LETKF in
comparison with current, nudging-driven forecasts.
24
Data Assimilation
Ensemble data assimilation for regional reanalyses
L.Bach(1), C.Schraff(2), J.Keller(2, 3), A.Hense(1)
(1) Meteorological Institute, University of Bonn, Germany,
(2) Deutscher Wetterdienst, Germany,
(3) Hans-Ertel-Centre for Weather Research, Germany
A new development in the field of regional reanalyses is the incorporation of uncertainty
estimation. In the framework of the climate monitoring and diagnostics branch of the HansErtel Centre for Weather Research (HerZ-TB4) and the FP-7 funded project Uncertainties in
Ensembles of Regional Reanalyses (UERRA) we develop and experiment with ensemble data
assimilation combined with other ensemble generation techniques to identify a method capable
of yielding a comprehensive uncertainty estimation of the atmospheric trajectory in the past.
The most uncertain ingredients of systems employed for the production of regional reanalyses
are the assimilated observations, the lateral boundary conditions as well as uncertainties in
the model physics. Since the 1-member realization reanalyses (Bollmeyer et. al, 2015) produced
during the first phase of the Hans-Ertel-Centre for Weather Research are based on nudging(e.g.
Schraff,1997), we have initially developed a technique to estimate the uncertainty of a nudging
reanaylsis given observation uncertainties. This technique is denoted ensemble nudging.
To estimate the impact of lateral boundary condition uncertainty, perturbed lateral boundary
conditions can be employed, e.g. provided by an ICON-ensemble or the new global ensemble
reanalysis ERA-5 by ECMWF. To incorporate model error, ensemble nudging can be combined
with a perturbed physics ensemble generation technique as similarly used by COSMO-LEPS or
with stochastic perturbation of physical tendencies (SPPT).
Further ensemble data assimilation techniques that we contemplate are the newly developed
KENDA-LETKF (Schraff, 2015, submitted) as well as a hybrid combination of the LETKF with
ensemble nudging.
We present case studies for the European Cordex domain CORDEX-EUR11 performed with
COSMO at 12 km grid spacing. The evaluation focuses on a comparison of the probabilistic and
uncertainty estimation capabilities of the different methods and their usefulness for the purpose
of producing regional reanalyses.
Invited Speaker
A review on regional convection permitting climate modeling
Nicole van Lipzig, Andreas Prein, Erwan Brisson, Kwinten Van Weverberg,
Matthias Demuzere, Sajjad Saeed, Martin Stengel
(1) Department of Earth- and Environmental Sciences, KU Leuven,
(2) and the CLM-Community working group CRCS
With the increase of computational resources, it has recently become possible to perform
climate model integrations where at least part the of convection is resolved. Since convection
Data Assimilation
25
permitting models (CPMs) are performing better than models were convection is parameterized,
especially for high-impact weather like extreme precipitation, there is currently strong scientific
progress in this research domain (Prein et al., 2015). Another advantage of CPMs, that have
a horizontal grid spacing <4 km, is that they better resolve complex orography and land use.
The regional climate model COSMO-CLM is frequently applied for CPM simulations, due to
its non-hydrostatic dynamics and open international network of scientists. This presentation
consists of an overview of the recent progress in CPM, with a focus on COSMO-CLM. It consists
of three parts, namely the discussion of i) critical components of CPM, ii) the added value of
CPM in the present-day climate and iii) the difference in climate sensitivity in CPM compared to
coarser scale models. In terms of added value, the CPMs especially improve the representation of
precipitation’s, diurnal cycle, intensity and spatial distribution. However, an in depth-evaluation
of cloud properties with CCLM over Belgium indicates a strong underestimation of the cloud
fraction, causing an overestimation of high temperature extremes (Brisson et al., 2016). In terms
of climate sensitivity, the CPMs indicate a stronger increase in flash floods, changes in hail
storm characteristics, and reductions in the snowpack over mountains compared to coarser scale
models. In conclusion, CPMs are a very promising tool for future climate research. However,
additional efforts are necessary to overcome remaining deficiencies, like improving the cloud
characteristics. This will be a challenging task due to compensating deficiencies that currently
exist in ‘state-of-the-art’ models, yielding a good representation of average climate conditions.
In the light of using CPMs to study climate change it is necessary that these deficiencies are
addressed in future research. Coordinated modeling programs are crucially needed to advance
parameterizations of unresolved physics and to assess the full potential of CPMs.
References:
Brisson, E., K. Van Weverberg, M. Demuzere, A. Devis, S. Saeed, M. Stengel, N.P.M. van
Lipzig, 2016. How well can a convection-permitting climate model reproduce 1 decadal statistics
of precipitation, temperature and cloud characteristics? Clim. Dyn. (minor revisions).
Prein, Andreas F., Wolfgang Langhans, Giorgia Fosser, Andrew Ferrone, Nikolina Ban, Klaus
Goergen, Michael Keller, Merja Tölle, Oliver Gutjahr, Frauke Feser, Erwan Brisson, Stefan
Kollet, Juerg Schmidli, Nicole P. M. van Lipzig, Ruby Leung. (2015) A review on regional
convection-permitting climate modeling: Demonstrations, prospects, and challenges. Reviews of
Geophysics 53:10.1002/rog.v53.2, 323-361.
26
Surrogate climate change sensitivity studies with
convection-resolving models: The diurnal cycle of summer
convection over the Alps
Michael Keller (1, 2), Oliver Fuhrer(3), Nico Kröner(1), Juerg Schmidli (1, 4),
Reto Stöckli(3), Christoph Schär(1)
(1) Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland,
(2) Center for Climate Systems Modeling (C2SM), ETH Zürich, Zurich, Switzerland,
(3) Federal Office of Meteorology and Climatology MeteoSwiss, Zurich, Switzerland,
(4) Institute for Atmospheric and Environmental Sciences, Goethe University, Frankfurt am
Main, Germany
Climate models project an increase in heavy precipitation events for future climate. One important element of such events is convection, which is poorly represented in models with parameterized convection. In this study, simulations with 12 km horizontal grid spacing (convectionparameterizing model, CPM) and 2 km grid spacing (convection-resolving model, CRM) are
employed to investigate the change in the diurnal cycle of convection with warmer climate. For
this purpose, simulations of 11 days in June 2007 with a pronounced diurnal cycle of convection
are compared with surrogate simulations from the same period. The surrogate climate simulations mimic a future climate with increased temperatures, but unchanged relative humidity
and synoptic-scale circulation. Two temperature scenarios are compared, one with homogeneous
warming (HW) using a vertically uniform warming, the other with vertically-dependent warming
(VW) that enables changes in lapse rate.
For CRM, an increase of hourly heavy precipitation events is found for both surrogate scenarios. The intensification is consistent with the Clausius-Clapeyron relation. For cloud type
frequencies, virtually no changes are found for HW, but substantial reduction in high clouds is
found for VW. Some of the CPM results differ significantly. Importantly, the increase of heavy
precipitation events simulated by CPM is beyond the Clausius-Clapeyron relation. Moreover,
significant differences between CPM and CRM are found, which are larger than between surrogate and control simulations. This includes in particular differences in the timing of the diurnal
cycle of convection, frequency of precipitation with low intensities, surface runoff, soil moisture
and top of the atmosphere energy budgets.
27
Large-scale secondary circulations in the COSMO-CLM
N. Becker(1), U. Ulbrich(1), R. Klein(2)
(1) Institut für Meteorologie, Freie Universität Berlin,
(2) Institut für Mathematik, Freie Universität Berlin
Regional climate models (RCMs) are used to add smaller scales to coarser resolved driving
data. However, RCMs do not only add smaller scales, but also deviate from the driving data
on larger scales. In this work large scale deviations between RCM simulations and the driving
global model data are analyzed. The aim is to uncover the driving mechanisms of large scale
circulation anomalies in the RCM. A 40-year COSMO-CLM simulation at a resolution of 0.165◦ ,
as well as a series of 1-month COSMO-CLM simulations with different domains over Europe, is
analyzed. The simulations were forced with a 1.875◦ resolution ECHAM5 simulation.
The differences of the temporally averaged wind vector fields between the RCM and the driving
GCM simulation show large scale vortices, which are referred to as the secondary circulation
(SC). A cluster analysis shows that, in particular in winter, the SC depends strongly on the
large scale flow conditions within the RCM domain. Anticyclonic SC vortices with more than 6
m/s are found downstream of the Alps. The vortices vertically cover the whole troposphere and
also affect the pressure and temperature profiles. Simulations with successively shifted model
boundaries show, that the SC strongly depends on the chosen model domain. A reduction of
the horizontal resolution, as well as the application of the spectral nudging technique, lead to a
weakening of the SC.
Apparently, the large scale circulation prescribed by the driving data is modified by the
different representation of orographic effects in the RCM and GCM. Those modifications cannot
exit the RCM domain due to the prescribed lateral boundary conditions but, instead, have to
be balanced within the RCM domain as seen in the SC fields. Although only one specific RCM
was considered, the underlying mechanisms suggest that the SC can be regarded as a common
feature of one-way nested RCMs with prescribed inflow and outflow conditions. The SC has the
potential to produce systematic large-scale biases in RCMs and, therefore, a consideration of
the SC in the process of RCM evaluation is highly recommended.
Update frequency of the driving data as a source of error at the
lateral boundaries in long term and short term simulations
Klaus Pankatz and Astrid Kerkweg
University of Mainz
The work presented was part of the joint project “DecReg” (“Regional decadal predictability”)
which was in turn part of the project “MiKlip” (“Decadal predictions”), an effort funded by the
German Federal Ministry of Education and Research to improve decadal predictions on a global
and regional scale.
In Module C of MiKlip, one big question is if regional climate modeling shows “added value”,
i.e. to evaluate, if regional climate models (RCM) produce better results than the driving models.
The scope of this study is to look more closely at the setup specific details of regional climate
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modeling. As regional models only simulate a small domain, they have to inherit information
about the state of the atmosphere at their lateral boundaries from external data sets. There are
many unresolved questions concerning the setup of lateral boundary conditions (LBC).
External data sets come from global models or from global reanalysis data-sets. A temporal
resolution of six hours is common for this kind of data. This is mainly due to the fact, that
storage space is a limiting factor, especially for climate simulations. However, theoretically, the
coupling frequency could be as high as the time step of the driving model. Meanwhile, it is
unclear if a more frequent update of the LBCs has a significant effect on the climate in the
domain of the RCM.
The first study examines the long term effects of the update frequency. The study is based on
a 30 year time slice experiment for three update frequencies of the LBC, namely six hours, one
hour and six minutes. The evaluation of means, standard deviations and statistics of the climate
in the regional domain shows only small deviations, some statistically significant though, of
2m temperature, sea level pressure and precipitation. The second part of the first study assesses
parameters linked to cyclone activity, which is affected by the LBC update frequency. Differences
in track density and strength are found when comparing the simulations.
The second study assesses the development of short term effects of the update frequency
due to a non-physical perturbation of the LBC. A series of short 90-day long experiments are
carried out: A non-physical perturbation is added to the temperature and the pressure field at
the lateral boundaries. Each experiment varies in strength, location and point in time of the
perturbation. The experiments are compared to a control simulation. As the realizations begin
to differ a pattern of higher and lower errors emerges which is highly correlated to the strength
of the forcing at the boundaries. However, the magnitude of the error is independent of the type
and the strength of the perturbation. Three types of deviation propagation are found: Soundwaves, gravity waves and an advective component. A passive tracer is introduced together with
the perturbation. The propagation of this tracer contains information on the advective part of
the deviation propagation. It can be shown that after a couple days a dynamical equilibrium
between the deviations inside the regional domain and the driving data is reached. The dynamical
equilibrium depends on the strength of the forcing. However, the seasonality of the forcing exhibit
only a slight influence on the strength of the deviations.
Complementing and analyzing the CORDEX-EUR11 Ensemble
Steger, C., J. Brauch and B. Früh
The latest generation of climate projections for the 21st century are build on new emission
scenarios based on Representative Concentration Pathways (RCPs). Within the world wide coordinated effort of the Coupled Model Intercomparison Project Phase 5 (CMIP5), their impact
on climate is simulated with global models of the climate system. A sample of the global simulations is dynamically downscaled for Europe in the framework of EURO-CORDEX. Many
members of the COSMO-CLM Community have already contributed to this major project. Further simulations, based on both dynamical and statistical methods, with focus on Germany
and the river catchments draining into Germany, are conducted within the framework of the
project ReKliEs-De to account for the full range of model variability. Here we present results
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from the first COSMO-CLM simulation with boundary conditions from the global climate model
MIROC5. A comparison with observation data and existing simulations shows, that the model
chain MIROC5 – CCLM performs well over the CORDEX-EU domain, especially in the central part. Furthermore, we present first results from the unique set of high resolution climate
change simulations for Europe, which results from the experiments conducted in CORDEX and
ReKliEs-De.
Long term wind farm induced changes over the north sea
Fabien Chatterjee(1), Nicole van Lipzig(1), Johan Meyers(2)
(1) Department of earth and environmental sciences, University of Leuven, Belgium,
(2) Department of mechanical engineering, University of Leuven, Belgium
Offshore wind deployment is foreseen to expand dramatically and solid progress has been
made towards 40 GW of offshore wind by 2020 (http://www.ewea.org/policy issues/offshore/
(2015)). This expansion is strongly driven by EU and national policies that aim to provide a
higher penetration of renewable energy sources.
Such an increase in wind farm deployment is likely to affect the climatology around the wind
farms. Such impacts are investigated by comparing two ten year simulations (1999-2008) using COSMO4.8-clm19, over the North Sea with a domain centering on the FINO 1 platform.
COSMO-CLM has been evaluated for winds using data from QUIKSCAT scatterometer and the
FINO1. A state of the art wind farm parameterisation is implemented in COSMO-CLM. Cloud
cover and precipitation is found to increase over the wind farms and decrease in the surrounding
areas. The mechanisms behind this, notably changes in moisture fluxes, are investigated. Furthermore, a wind park can hinder the flow attaining another park behind it therefore affecting
its power production, and the extent of this is quantified.
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Urban effects on summertime air temperature in Germany under
climate change
S. Schubert(1), S. Grossman-Clarke(2), D. Fenner(3)
(1) Geography Department, Humboldt-Universität zu Berlin,
(2) Potsdam Institute for Climate Impact Research,
(3) Chair of Climatology, Department of Ecology, Technische Universität Berlin
The impact of climate change on urban relative to rural summertime air temperatures is investigated for nine major cities in Germany, under the Representative Concentration Pathway
trajectory 8.5. The analysis is based on simulations of representative historical and projected
future summers with COSMO-CLM in conjunction with the multilayer urban parametrization
DCEP when driven by three global circulation models (GCM). Each GCM provides boundary conditions for two historical and two future summers that resemble average conditions for
Germany for the periods 1976–2005 and 2031–2060, respectively. The simulations show climate
change signals (CCS) in summer mean urban-rural air temperature differences of the city ensemble of up to 0.15K. Across all driving GCMs, the largest changes are projected for the city
of Berlin. Characteristics of the diurnal courses of urban-rural air temperature differences, the
magnitude of the CCS and its physical reasons are GCM specific. Specifically, CCS are caused either by positive or negative changes in the Bowen ratio of the rural boundary with little changes
in the urban surface fluxes, or vice versa. The study emphasizes the importance of the driving
GCM in COSMO-CLM simulations when investigating urban effects on air temperature under
global climate change.
Impact of model resolution and urban parametrization on urban
climate simulation: a case study for Zurich
Gianluca Mussetti(1, 2), Dominik Brunner(1), Stephan Henne(1), Jonas
Allegrini(2, 3), Hendrik Wouters(4), Sebastian Schubert(5), Jan Carmeliet(2, 3)
(1) Laboratory for Air Pollution/Environmental Technology, Empa, Switzerland
(2) Laboratory for Multiscale Studies in Building Physics, Empa, Switzerland
(3) Chair of Building Physics, ETH Zurich, Switzerland
(4) Dept. Earth and Environmental Sciences, KU Leuven, Belgium
(5) Geography Department, Humboldt University Berlin, Germany
An increasing number of people is living in cities where they are exposed to the specific urban
weather and climate conditions. Understanding and predicting these conditions (e.g. the urban
heat island effect) is therefore of growing importance. Mesoscale models are effectively used to
simulate urban atmospheric conditions at kilometer-scale resolutions making use of sub-grid scale
parametrizations that consider modifications of the land surface and heat emissions by human
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activities. However, at this resolution, the urban area of medium size cities is represented by only
very few grid cells. In order to better capture the heterogeneity within and surrounding such
cities and the corresponding impact on local climate condition, urban climate models should be
used at sub-kilometer resolution.
The mesoscale weather and climate model COSMO in CLimate Mode (CCLM) is used in this
study to investigate the impact of model resolution and urban parametrization on urban climate
modelling. Two urban parametrizations with a different level of complexity are used, the urban
land surface model TERRA-URB and the Double-Canyon Radiation Scheme (DCEP). TERRAURB uses a simple and efficient bulk approach to consider the impact of urban areas. DCEP
employs a more complex multi-layer scheme that includes an accurate description of radiation
interactions between different surfaces within the urban canopy. CCLM is used, together with
the urban parametrizations, at various horizontal resolutions of: 2 km, 1 km and 500 m. The
simulations are performed over the orographically complex Zurich metropolitan area during an
intense heat wave event in summer 2015. MeteoSwiss operational COSMO-2 analyses are used
as initial and boundary conditions.
The model results are evaluated using available surface observations located within and in
proximity to the urban area. Generally, the modelling system is able to reproduce the spatial
and temporal evolution of the urban heat island in the modelling domain. The performance
at different model resolutions is compared in terms of urban heat island modelling and flow
modifications. Preliminary considerations are made on the strengths and weaknesses of each
urban parametrization and on the advantages of high resolution. Finally, directions for further
developments are suggested.
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Poster 20: Assimilation of KITcube observations in
high-resolution COSMO simulations
Gregor Gläser(1), Peter Knippertz(1), Norbert Kalthoff(1), Corinna Hoose(1),
Samiro Khodayar(1), Andreas H. Fink(1), Martin Kohler(1), Christian
Barthlott(1), Jan Handwerker(1), Vera Maurer(1), Bianca Adler(1), Leonhard
Gantner(1), Andreas Wieser(1), and Andreas Kopmann(2)
(1) Institute of Meteorology and Climate Research - Troposphere Research (IMK-TRO),
(2) Institute for Data Processing and Electronics (IPE)
KITcube is an advanced, mobile, integrated observation system developed at the Institute
of Meteorology and Climate Research – Troposphere Research (IMK-TRO) of the Karlsruhe
Institute of Technology (KIT). Including a suite of remote sensing instruments such as cloud
and precipitation radars and Doppler lidars, the KITcube allows temporally and spatially highly
resolved measurements within a volume of about 10 x 10 x 10 km2 . IMK-TRO aims at a closer
linkage of KITcube’s observational data with numerical weather prediction (NWP) models for
comparison and assimilation purposes. Assimilation of data from field campaigns, e.g., Germany
in 2013, Israel in 2014 and West Africa in 2016, have high potential to improve simulations within
model domains around the KITcube measurement volume. In simulations with grid spacings
between 100 and 1000 m, KITcube data cover 100 to 10000 horizontal grid points and all levels up
to 10 km. The availability of measurements and simulations with such high resolutions allows for
new insights into and a better understanding of the processes on these scales. The primary focus
of KITcube campaigns is currently on the planetary boundary layer and convective processes
but could be extended to cloud microphysics, aerosols and air chemistry in the future.
The recent development of the Kilometer-Scale Ensemble Data Assimilation (KENDA) for
COSMO at the German Weather Service (DWD) offers a great opportunity and some first steps
are currently being taken to integrate KITcube data into this system. The technical practicability
has already been shown for standard variables such as 2-m temperature and 10-m wind. The
conversion of KITcube’s raw data into a COSMO-readable format (cdfin-files) is one major issue
during the initial phase of this initiative. At the conference, the status-quo of this work and some
first results of assimilated high-resolution simulations in Germany during the HOPE campaign in
2013 will be presented. In the longer run, the diversity of the KITcube instrumentation requires
the development of new forward operators, e.g. for sensible heat and momentum fluxes or drop
size distributions in order to exploit the full potential of this measurement platform.
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Poster 22: Assimilation of data from conventional and non
conventional networks through a Local Ensemble Transform
Kalman Filter scheme in the COSMO model
Mario Corbani(1), Chiara Marsigli(2), Virginia Poli(2), Tiziana Paccagnella(2)
(1) Department of Physics and Astronomy of the University of Bologna,
(2) ARPA Emilia-Romagna - Hydro-Meteo-Climate Service
The work deals with the data assimilation for the 2.8 km COSMO model over Italy using
the Kilometer-scale ENsemble Data Assimilation system (KENDA) LETKF scheme. The aim of
the work is to study the impact of the assimilation of two different types of data: temperature,
humidity, pressure and wind data from conventional networks (SYNOP, TEMP, AIREP) and
3d reflectivity from radar volume.
The selected period for the experiments is one week in October 2014, including 9 and 13
October, when two major flood events took place over Northern Italy. A continuous assimilation
cycle is implemented with 3-hourly step, with Boundary Conditions (and Initial Conditions for
the cold start) from ECMWF ENS, 20 members.
Three experiments are performed: 1) assimilation of data from conventional networks (SYNOP,
TEMP, AIREP) using adaptive multiplicative inflation and relaxation to prior perturbations
inflation (RTPP) only, 2) addition of stochastically perturbed parametrization tendencies scheme
(SPPT) for model perturbation in each COSMO run, 3) assimilation of data from conventional
networks together with reflectivity data from radar volumes.
Objective evaluation of the experiments is carried out with the methodologies available in the
KENDA package or developed at ARPA-SIMC: compute the Desroziers statistics for SYNOP,
TEMP and AIREP, over the entire domain as well as selected areas, objective verification (bias
and rms error) of analysis and first guess ensemble means of temperature at the lowest model level
against SYNOP data of 2mT (not assimilated), over the entire domain as well as selected areas,
objective verification of a deterministic COSMO forecast which uses the KENDA deterministic
analysis as Initial Conditions. Verification of the deterministic run is performed in terms of
near-surface weather parameters (total precipitation, 2mT, MSLP) over the entire domain and
over Northern Italy only. Spectra of the KENDA analyses (all members) are also computed for
temperature and humidity fields at few model levels (the lowest and a few level in the vertical).
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Poster 24: Status of the COMET (Italian Operational
Meteorological Center) Ensemble Data Assimilation and Forecast
System
Francesca Marcucci(1), Lucio Torrisi(1), Valerio Cardinali (1, 2)
(1) COMET-Italian Operational Met Center, Pratica di Mare, Italy
(2) EUMETSAT
An ensemble data assimilation algorithm based on the LETKF scheme (the so called CNMCALETKF)has been operationally running, since june 2011 at the Italian Meteorological Center.
Recently, the COSMO KENDA code has been implemented in order to include a few CNMCALETKF features and implement the assimilation of soil moisture. Comparison between the two
systems and the impact of the different features will be showed.
Poster 26: Simulation of severe convective storms by the
COSMO NWP model
Z. Sokol, P. Pesice, V. Bliznak, P. Zacharov
Institute of Atmospheric Physics Czech Academy of Sciences
We applied the COSMO NWP model with the assimilation of radar reflectivity data to nowcasting of severe convective precipitation. The model was applied with a horizontal resolution
of 2.8 and 1.1 km and with one and two moment microphysics. The precipitation forecasts were
evaluated against the estimates of real precipitation obtained by merging radar-derived precipitation and rain-gauge measurements. We also evaluated forecasted development of convective
storms using synthetic satellite imagines of Meteosat Second Generation (MSG) and compared
them with real satellite MSG measurements for 8 spectral channels in infrared part of the electromagnetic spectrum.
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Poster 28: Assimilation of surface observations in KENDA and
observation impact on the convection-permitting scale
T. Necker(1), D. Leuenberger(2), M. Weissmann(1), M. Sommer(1)
(1) Hans-Ertel-Centre for Weather Research: Data Assimilation Branch,
(2) MeteoSchweiz
The assimilation of 2m humidity and 2m temperature offers a great potential for convectivescale data assimilation. An accurate representation of near-surface variables influences the characterization of the planetary boundary layer and can have a significant impact on e.g. the
initiation of convection or the simulation of fog. So far, the Km-scale ENsemble Data Assimilation (KENDA) system within COSMO does not make sufficient use of surface observations. 2m
humidity is only used in the nudging data assimilation scheme and 2m temperature is not used
at all.
The goal of this study is to improve the COSMO near-surface analysis by making better
use of screen height observations in the KENDA data assimilation system. To this end, single
observation experiments are carried out using the MeteoSwiss COSMO-LETKF system with a
mesh-size of 2.2km. We investigate the influence of surface humidity assimilation on the analysis
and its sensitivity to various settings, such as the horizontal and vertical localization lengths in
different meteorological situations.
Besides the assimilation experiments, a method for an ensemble-based approximation of observation impact using an observation-based verification metric was developed in the framework of
the Hans-Ertel Centre for Weather Research (HErZ). Recently, the method was adapted to use
independent radar-derived precipitation for verification and first results of the impact assessment
using precipitation fields for verification are presented.
Poster 30: Spurious convection in dynamically imbalanced radar
data assimilation
Matthias Schindler(1), Heiner Lange(2), Christian Keil(1)
(1) Meteorological Institute Munich (MIM),
(2) Hans Ertel Centre for Weather Research (HERZ)
In the idealized COSMO-KENDA radar data assimilation experiments of Lange & Craig 2014,
mid-latitude organized convection was assimilated, and spurious convection arose in the forecast
ensemble.
Employing Lagrangian Particle Tracking the dynamical nature of spurious convective cells in
the nature run as well as in the ensemble forecasts is investigated. Results should lead towards the
identification of data assimilation properties that may cause damage to the dynamical balance
of the forecast model.
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Poster 40: Dynamics change of atmospheric precipitation in the
context of climate change in Syunik region of the Republic of
Armenia
Varduhi Margaryan(1), Larisa Simonyan(2)
(1) Yerevan State University,
(2) Armstatehydromet
Atmospheric precipitation is one of the main climatic elements. It characterize the water balance of area is main source of moisture of land. Atmospheric precipitation has main role in runoff
formation. Atmospheric precipitation as well as other meteorological elements is distinguished
by regularities of spatiotemporal distribution. So, discovering and evaluation of regularities of
spatiotemporal distribution of atmospheric precipitation (especially in the conditions of global
climate change), evaluation of risk and vulnerability, productive management, reliable forecasting
and warning on time, prevention and neutralization of negative effects of change, development of
fast response system, information and education level of population is an important precondition
of people’s security, also of stable development of the republic.
Taking account the role and significance of precipitation in the conditions of our low-water
country, accumulation and using the water in height-water season, for productive using and
planning of water resources in the work is studied and evaluated the regime of atmospheric
precipitation of Syunik, the regularities of spatiotemporal distribution in the context of climate
change, to work out the ways of productive management. For it in this work solved the following
problems: to collect, work out and analysis the result of observation of atmospheric precipitation
of Syunik; to discover and analysis the features of spatiotemporal regularities of precipitation of
region.
For solving this problems in this work as a theoretical base is appropriate studies, resolutions
of government of the RA, reports of appropriate services, as a raw material-long-term observation of actual data of 6 meteorological stations of studying area (1913-2014), which are stored
in Armstatehydromet of MES of RA. As a methodological basis used mathematic-statistical,
geographical, extrapolation, analysis, correlation, complex methods.
The Syunik region locates in the south-eastern part of RA. It is the region with the most
mountainous and with the biggest difference of surface height. Studying area is the second area
by the size of territory (4506 sq.km), which is a 15 % of the territory of RA. And vice versa,
Syunik has a little number of population (164.1 thou. Inhabitant). In the region annual rainfall
in average changes within 266-737mm.
In the republic have done many researches, but still absent systemized studies of discovering
of reasons of changes of precipitation, and existing studies refer to individual parties only. So,
advisable to continue systemized and complex studies of runoff and develop future forecasts of
its change using new models.
In the result of studies have got the following conclusions and suggestions:
• The atmospheric precipitation is characterized by regularities of spatiotemporal changes;
37
• Because of complicated orographic features studying region was distinguished several regions of precipitation distribution (Vorotan river basin, Sisian region, Goris region, Voghchi
river basin, Meghri river basin);
• In region Goris region is distinguished by moisture, and Sisian and Meghri by dryness;
• There is a suggestion to accumulate the water of high-level basin of comparatively moist
period for its using in low-level and foothills dry areas;
• There is a tendency of decreasing of atmospheric precipitation, except of Sisian and Goris
regions.
Are necessary:
• comprehensive, systematic and continuous observations;
• providing of meteorological stations with modern equipment (especially automatic);
• to accumulate the water of high-level basin of comparatively moist period for its using in
low-level and foothills dry areas;
• evaluation of the vulnerability of ecosystems as a result of changes in atmospheric precipitation;
• developing of notification of population about the climate change;
• implementation of organizational, legal, institutional, technical measures to mitigate climate change and adapt the economy to new environmental conditions;
• strengthening of scientific studies of climatic problems and implementation of new technologies;
• realization legal-organization, institutional, technical arrangements for adaptation of economy to new natural conditions and soften of climate change consequences;
• working out of real climatic scenarios;
• working out of the programs for softening the negative effects of climate change;
• working out are and implementation of qualification programs, organization of studying
processes, development of specialists’ qualification;
• providing of modern ways of availability and outspread of information;
• providing of international scientific-educational cooperation, strengthening of inter-agency
cooperation.
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Poster 42: Stochastic perturbations representing the mechanical
effect of subgrid-scale orography
F. Brundke, K. Kober, G. Craig
Meteorologisches Institut München
A recently introduced stochastic boundary layer perturbations scheme aims for representing
small-scale variability due to unresolved physical processes. This basic version of the scheme
represents variability in convective boundary layers due to turbulence driven by surface heating.
In this study this scheme is extended to represent another process relevant in the initiation of
convection. The creation of variability in vertical velocity by the interaction of the horizontal
flow with the subdgrid-scale orography (SSO) is considered.
The vertical displacement is calculated on basis of the internal gravity wave formalism and
a high resolution SSO data set. Depending on the average stability of the boundary layer, the
amplitude of the perturbations is determined and scaled with the steepness of the orography
and the intensity of the horizontal wind.
Simulations with the SSO perturbations scheme lead to a drier, cooler boundary layer and
moister, warmer regions with more condensation at higher levels compared to unperturbed reference simulations for different case studies representing weak large-scale forcing. A comparison
based on root mean squared error and domain averaged hourly precipitation rates of the resulting
precipitation forecast with radar observations shows that a small improvement of the precipitation forecast can be achieved in situations with weak large-scale forcing. These improvements
strongly depend on the characteristics of the orography within the investigated area.
Poster 44: Potential Vorticity anomalies associated with deep
moist convection
Chris Wejienborg(1), Jeffrey Chagnon(2), Petra Friederichs(1), Suzanne Gray(3),
Andreas Hense(1)
(1) Meteorological Institute, University Of Bonn,
(2) Earth, Ocean and Atmospheric Science, Florida State University,
(3) Department of Meteorology, University of Reading
Severe weather extremes like extreme rainfall are often not well covered by numerical weather
prediction models. The WEX-MOP (Mesoscale weather extremes: Theory, spatial modeling and
prediction) project aims at improving the forecast of those extremes, using data of the nonhydrostatic COSMO-DE.
Potential vorticity (PV) received not much attention on the convective weather scale. PV is
tied to the balanced structure of the flow and has been useful in describing synoptic scale processes like cyclogenesis. Deep moist convection is per definition unstable, and therefore balance
is not directly expected on the convective weather scale. We hypothesize that PV anomalies on
the convective weather scale might still be “quasi-balanced”. Moreover, even when PV is not
conserved, PV might still be useful to indicate the importance of diabatic processes.
39
To test our hypothesis we created a climatology of PV dipoles associated with storm cells. To
accomplish this, we use a tracking algorithm applied to maxima of the vertical velocity during
9 severe weather cases in COSMO-DE. Composites show that even when averaging over 3165
storm cells a clear PV dipole pattern is visible. This is consistent with theory and with related
structures in the mass and momentum fields and could be termed a statistical balance. Intense
convective cells, measured by e.g. precipitation rates, show a monopole “supercell” structure. We
also discuss the possible use of PV as a predictor of severe weather.
POSTER: Clouds, Chemistry,
Aerosol and Radiation
Poster 12: Shallow convection scheme and its deficits
Tobias Schad, Bernhard Vogel
Karlsruhe Institute of Technology (KIT)
The model system COSMO-ART has been used to simulate stratocumulus cloud decks in the
south east pacific to investigate aerosol-cloud-interactions for this specific type of clouds. The
effects of artificially introduced sea salt particles on cloud microphysics and radiation budget,
also known as marine cloud brightening, is examined as this is one imaginable technique for
climate engineering to postpone global warming.
Basic idea of this type of climate engineering is to artificially release particles which act as
additionally cloud condensation nuclei (CCN), which lead to higher cloud droplet numbers,
which increases cloud albedo (Latham et. al, 2008) which is very effective in persistent maritime
boundary layer clouds. The region in the south east pacific is known to be characterized by a
persistent layer of stratocumulus clouds and their existence is a result of a complex chain of
interactions between several processes. Due to the complexity of the system and that processes
take place on very small scales atmospheric models encounter difficulties in capturing this cloud
layer in a realistic way. Additionally there are still uncertainties in the outcome of this method
due to uncertainties in cloud aerosol interactions.
Simulations with a horizontal resolution of 2.8km showed relatively good performance according to observations, but one major drawback were the representation of the vertical profiles of
specific humidity. Although they showed a good agreement according to the height of the boundary layer, profiles underestimated specific humidity in the lower levels up to 2 g/kg. Another
major drawback was the underestimation of vertical integrated grid-scale cloud liquid water
content. Since clouds in this simulation are mainly shallow clouds the shallow convection parameterization is a major component in simulating these clouds respectively the cloud liquid
water content.
By switching off the shallow convection parameterization the results of the simulations could
be improved. Although the height of the boundary layer is now underestimated few meters the
profile of the specific humidity fits more to observations. Also the vertical integrated grid-scale
cloud liquid water content is in a better agreement with observations.
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It could be shown that in case of the shallow convection parameterization switched on a
major part of the liquid cloud water content is produced by the convection scheme. This scheme
is not able to take aerosol as CCN into account which is a major deficiency in investigating
aerosol-cloud-interaction and investigating the effects of marine cloud brightening because this
also affects the radiation budget.
The conclusion is that the shallow convection parameterization in its actual configuration is
not able to reproduce the vertical profiles of for example specific humidity and is also not able
to take into account direct effects of changes in aerosol loading which is a major drawback in
investigating aerosol-cloud-interaction and could disguise potential aerosol-effects.
Poster 14: Influence of the turbulence and convection
parameterization on convective initiation in kilometer-scale
simulations
S. Böing (1, 3), O. Fuhrer(2), G. DeMorsier(2), C. Schär(1), J. Schmidli (1, 4)
(1) ETH, Institute for Atmospheric and Climate Science, Zürich, Switzerland,
(2) MeteoSwiss, Zürich, Switzerland,
(3) University of Leeds, Institute for Climate and Atmospheric Science, Leeds, UK,
(4) Goethe University, Institute for Atmospheric and Environmental Sciences, Frankfurt am
Main, Germany
The next generation of numerical weather prediction models will run with a grid spacing of
about 1 kilometer. Deep convection is coarsely resolved at this grid spacing, but shallow clouds
and boundary layer turbulence are too small to be resolved. Previous experience with NWP at
MeteoSwiss and other institutions has shown significant biases at this resolution: shallow clouds
tend to be underrepresented and a too sudden onset of deep convection occurs. We use idealized
simulations to investigate the ability of a kilometer-scale NWP model (COSMO) to accurately
represent the initiation and development of moist convection. In particular, we look into the
role of boundary layer turbulence, horizontal mixing and the convection scheme. We do this
by systematically exploring a number of case studies (GEWEX Cloud System Study (GCSS)
cases as well as two previously documented cases of convection over topography), using both the
kilometer-scale resolution setup and an LES setup with higher resolution. Using the latter setup
as a reference, we aim to identify weaknesses and suggest improvements in the formulation of
moist convection and turbulence. We look into the spatial distribution of turbulence, clouds and
precipitation and use conditionally sampled statistics to investigate the properties of clouds and
flow patterns. The standard convection scheme in COSMO captures the onset of clouds, but the
liquid water content and mass-flux near cloud top are overestimated. This behavior can be improved with modifications in the closure, convective triggering and the entrainment-detrainment
formulation. The kilometer-scale model performs surprisingly similar to LES simulations, even
for phenomena which it only coarsely resolves, such as convective cold pools, slope flows and
marginally resolved updrafts. We further discuss the effect of the horizontal mixing formulation
and turbulence parameterization on the initiation and development of moist convection.
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Poster 16: The representation of radiation, clouds and
precipitation in a default COSMO-CLM simulation over
Antarctica
N. Souverijns(1), A. Gossart(1), I. Gorodetskaya(1, 2), S. Lhermitte(1), A.
Mangold(3), Q. Laffineur(3), N. P. M. Van Lipzig(1)
(1) University of Leuven, Heverlee, Belgium,
(2) Center for Environmental and Marine Studies (CESAM), University of Aveiro, Aveiro,
Portugal,
(3) Royal Meteorological Institute of Belgium, Uccle, Belgium
The surface mass balance of the Antarctic ice sheet is highly dependent on the interaction
between clouds and precipitation. Our understanding of these processes is challenged by the
limited availability of observations over the area and problems in Antarctic climate simulations
by state-of-the-art climate models. Improvements are needed in this field, as the Antarctic ice
sheet is expected to become a dominant contributor to sea level rise in the 21st century.
These issues are investigated using long-term observations available at the Princess Elisabeth
(PE) Antarctic station and the regional climate model COSMO-CLM. PE is located in the
escarpment area of Dronning Maud Land, East Antarctica (72◦ S, 23◦ E). Since 2009-2010, several
instruments were set up analyzing atmospheric and cloud-precipitation processes. The groundbased remote sensing instruments include a ceilometer (measuring cloud-base height and vertical
structure), a 24-GHz radar MRR (providing vertical profiles of radar effective reflectivity and
Doppler velocity), and a pyrometer (measuring effective cloud base temperature). An automatic
weather station provides boundary-layer meteorology (temperature, wind speed and direction,
humidity, pressure), as well as broadband radiative fluxes and snow height changes. This set
of instruments can be used to infer the role of clouds in the Antarctic climate system, their
interaction with radiation and their impact on precipitation.
Regional climate modeling over Antarctica has a high potential since there are limited observations over the area. The non-hydrostatic COSMO-CLM regional climate model, with advanced
cloud-precipitation parameterizations, has been chosen as a tool for studying radiation-cloudprecipitation interactions. However, the model has to be adapted to the specific conditions in
polar regions. As the first step, the model is executed in its default settings using ERA-Interim
as its initial and lateral boundaries for several case studies at a horizontal resolution of 0.22◦ by
0.22◦ over the whole Antarctic continent.
In this poster, an introduction to this new research project will be presented, including some
first integrations in the application of COSMO-CLM over Antarctica. Using PE observations, a
preliminary evaluation of the model will be performed, particularly focusing on cloud radiative
forcing and precipitation amounts..The first model tests will lay ground for preparing the longterm model simulations and a more in-depth model evaluation.
42
Poster 18: An assessment of the COSMO-CLM simulation of
surface mass balance processes over Antarctica
Alexandra Gossart(1), Niels Souverijns(1), Stef Lhermitte(1), Irina
Gorodetskaya(1)Jan Lenaerts (1, 2), Alexander Mangold(3), Quentin
Laffineur(3)and Nicole Van Lipzig(1)
(1) Katholieke Universiteit Leuven - University of Leuven, Heverlee, Belgium,
(2) Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The
Netherlands,
(3) Royal Meteorological Institute of Belgium, Uccle, Belgium.
Surface mass balance (SMB) strongly controls spatial and temporal variations in the Antarctic Ice Sheet (AIS) mass balance and its contribution to sea level rise. Constraining AIS SMB
remains problematic due to the scarcity of observational data and challenges climate modelling which in turn limits our current understanding the processes contributing to AIS SMB.
Particularly, a large uncertainty exists regarding the impact of drifting snow on local SMB
measurements.
This issue is investigated using long-term observations available at the Princess Elisabeth (PE)
station. PE station is located in the escarpment area of Dronning Maud Land, East Antarctica
(72◦ S, 23◦ E). Several instruments analyze atmospheric conditions, cloud and precipitation properties, as well as drifting snow. The ground-based remote sensing instruments include a ceilometer
providing attenuated backscatter profiles at 15-sec temporal resolution. These profiles can not
only be used for estimating cloud base heights, but also the top height of the drifting snow layer
during cloud-free conditions. Contribution of drifting snow to the local SMB can be estimated
using automatic weather station (AWS) measurements, which include boundary-layer meteorology (temperature, wind speed and direction, humidity, pressure), as well as broadband radiative
fluxes and snow height changes.
This project uses the observations to evaluate the regional climate model COSMO-CLM.
Here, we apply it for the first time to Antarctica to study the sensitivity of AIS SMB to its
components, precipitation, sublimation and erosion. In this poster we will present preliminary
model performance of the COSMO-CLM using a default model set up with horizontal resolution
of 0.22◦ by 0.22◦ and ERA-Interim as its initial and lateral boundaries. Our case studies will
focus on the days when strong drifting snow conditions were observed at PE. Additionally,
snowpack properties simulated by COSMO will be compared to the output of the Community
Land Model run offline for the period 1979-2014 with Era-Interim forcing
43
POSTER: Soil, Vegetation and
Ocean
Poster 1: Benefit from using atmosphere-ocean coupled systems
for summer dry bias of regional climate models over Central
Europe
Ha Thi Minh Ho-Hagemann(1), Matthias Gröger(2), Burkhardt Rockel(1),
Matthias Zahn(1), Beate Geyer(1), H.E. Markus Meier(2, 3)
(1) Institute for Coastal Research, Helmholtz-Zentrum Geesthacht, Germany
([email protected]),
(2) Swedish Meteorological and Hydrological Institute – SMHI, Sweden,
(3) Leibniz Institute for Baltic Sea Research Warnemünde, Germany
A precipitation dry bias over major mid-latitude continents is a common problem of many
atmospheric models. For Europe, several studies pointed out the dry bias problem of many
regional climate models (RCMs) in summer. In the present study we investigated the benefit
of using atmosphere-ocean coupled systems for the summer drying problem of regional climate
models over Central Europe for two RCMs, the COSMO-CLM (hereafter CCLM) and the RCA4.
For CCLM, the atmosphere-only experiment at a resolution of 0.44o is compared with an
experiment of the coupled system COSTRICE in which CCLM is coupled to an ocean and a
sea-ice model, which are specifically designed for the North and Baltic Sea regions. The coupling
ocean domain of the COSTRICE coupled system covers not only the Baltic Sea and the North
Sea as other coupled systems but also a part of the North Atlantic Ocean. For RCA4, the
atmosphere-only experiment at a resolution of 0.22o is compared with the coupled simulation
of RCA4-NEMO. The coupling domain of RCA4-NEMO restricts the North Sea to a northern
boundary set at 60oN but covers the entire Baltic Sea. CCLM and RCA4 are set up for the
EURO-CORDEX domain. The coupling impact on the dry bias is analyzed for summer (JJA)
seasonal means of 30 years (1979-2009) and especially for summer extreme precipitation. The
E-OBS data on the 0.5o grid are used to evaluate the model performance.
The comparisons show that benefit of the coupling is different for the considered time-scales.
For example, if we look at the long-term seasonal mean, the coupled and uncoupled simulations
are mostly identical, which is the case for CCLM and RCA4 as well. However, if extreme precipitation is considered, especially for the Northerly circulation type (when the air flow from
the North Atlantic Ocean passes the coupling domain – the North Sea), the simulations of the
COSTRICE coupled systems are generally improved compared to the CCLM atmosphere only
run. However, for RCA4, the benefit of coupling is unclear. The difference between RCA4 and
RCA4-NEMO is insignificant also for extreme precipitation. The different behaviour of these
two RCMs may be related to different sensitivities of the atmospheric model components to the
change of SST over the coupling domain. The size and exact location of the coupling domain
may be also an important issue, which should be investigated in a future study, e.g. by using a
larger coupling domain for RCA4-NEMO.
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Poster 3: Simulation of snow bands in the Baltic Sea area with
the coupled atmosphere-ocean-ice model COSMO-CLM/NEMO
Trang Van Pham (1, 2, 3), Jennifer Brauch(2), Barbara Früh(2), Bodo Ahrens (1,
3)
(1) Senckenberg Biodiversity and Climate Research Centre, Germany,
(3) Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt,
Germany
Wind-parallel bands of snow over the Baltic Sea area are common during late autumn and
early winter. The phenomenon occurs when cold air flows over the warm water surface, enhancing convection and leading to heavy snow fall. Six snowband events from 1985 to 2010 are
simulated by using the coupled atmosphere-ocean-ice model COSMO-CLM/NEMO. The model
resolution is reasonably high to capture the snowbands; the atmosphere model COSMO-CLM
has a horizontal grid-spacing of about 25 km and the ocean model NEMO of about 3 km.
The instability of the atmosphere is investigated by comparing the surface temperature and the
temperature at 850 hPa, so are the pressure system which could result in north easterlies or
easterlies, and the heat fluxes transferred from the ocean to the atmosphere. We also evaluated
our model’s temperature values with satellite-based data and precipitation patterns over sea
with cloud satellite images and achieved a good agreement. The model results showed that the
coupled system COSMO-CLM/NEMO well reproduced the snowband events with high contrast
of temperature between the surface and higher atmosphere layer as well as the sharp bands of
precipitation over the sea. On the other hand, COSMO-CLM forced by averaged sea surface
temperatures (SSTs) could not re-create the snowbands. We also observed the enormous heat
fluxes released by the ocean to the atmosphere during the days when snowbands occurred. The
results show that SSTs which are not provided by the global climate models are needed; and the
regional climate model gave good results when having sufficiently good quality SSTs from ocean
model.
Poster 5: Intercomparison of multi-model simulations of day
time boundary layer evolution-III
P. Shrestha(1), G. Vogel(2), Wolfgang Kurtz(3), Jan-Peter Schulz(2), M. Sulis(1),
C. Simmer (1, 4), S. Kollet (3, 4) and Harrie-Jan Hendricks Franssen(3)
(1) Meteorological Institute of Bonn (MIUB),
(2) Deutscher Wetterdienst,
(3) Institute for Bio- and Geosciences, Agrosphere (IBG-3), Research Centre Jülich,
(4) Centre for High-Performance Scientific Computing in Terrestrial Systems ABC/J
Geoverbund
Previously, we presented an inter-comparison of surface energy fluxes and day time boundary
layer evolution, using two modeling systems that share the same atmospheric component: (1)
45
COSMO-DE with the Terra Land Surface Model and (2) COSMO-DE coupled with CLM and
ParFlow (TerrSysMP).
The idealized study showed significant differences in modeled albedo and surface energy partitioning as a function of soil moisture, which affected the boundary-layer profile. The 2008 offline
real data study over Falkenberg, using Terra and CLM, showed that Terra consistently simulates
higher sensible heat flux over a range of soil moisture conditions, which could be attributed to
the missing shading effect by grass. On the other hand, CLM arrived at improved simulated
fluxes in comparison to the measurements, but a consistent seasonal model bias was observed in
the simulated soil moisture, suggesting the need of parameter tuning or improvement in model
physics. In this study, we extend the intercomparison between Terra and CLM to a time period
of multiple years (2008-2014) to investigate this seasonal bias. Additionally, we also introduce
TerrSysMP in the Parallel Data Assimilation Framework (TerrSysMP-PDAF) in an assimilation experiment of soil moisture observations to update the parameters of CLM for improved
predictions of the seasonal dynamics of soil moisture and the energy balance.
Poster 7: Soil-atmosphere interactions in the Mediterranean area
S. Helgert and S. Khodayar
Institute of Meteorology and Climate Research (IMK-TRO), Karlsruhe Institute of Technology
(KIT), Karlsruhe, Germany
In a warming climate an increase in the intensity and frequency of High Impact Weather
(HIW) and climate extremes is expected. Events like floods and extreme heat have a crucial
impact on human health and society. The ability to predict such events is still a great challenge
and exhibits many uncertainties in the weather forecast and climate predictions. In this respect
the missing knowledge about soil-atmosphere interactions and their representation in models is
identified as one of the main sources of uncertainty.
The soil moisture controls the partitioning of sensible and latent heat fluxes on the surface
and thereby influences the boundary-layer stability and the precipitation formation. The coupling between soil-moisture and precipitation and related processes is investigated for different
Mediterranean regions. In this context our research objective focuses on the role of local and
remote soil moisture and evapotranspiration anomalies on initiation and development of HIW.
Simulations with the COSMO model are conducted in subseasonal and seasonal time scales
and at 7 km and 2.8 km spatial resolution. Observational data are further used for process
understanding and model validation, for example CMORPH for precipitation and LSA-SAF for
evapotranspiration. For the identification of moisture sources the COSMO online trajectories
module is utilized. Furthermore sensitivity studies are performed to prove the impact of soil
moisture initialization scenarios (wet/dry conditions) on the simulation of the selected HIW.
46
Poster 9: The influence of new parameterization of water
transport in the soil on structure PBL
Grzegorz Duniec, Andrzej Mazur
Institute of Meteorology and Water Management, National Research Institute
Soil and atmosphere boundary layer (ABL) interact with each other and have an influence on
physical processes in soil and atmosphere.
If high quality numerical forecast of meteorological fields and vertical profiles is expected,
good representation of complex hydrodynamics of porous media in parameterization schemes
should be prepared.
It is known that the present parameterization schemes in almost every numerical meteorological model don’t give satisfactory results. Authors prepared preliminary description of vertical
water transport in soil layers. New solutions was implemented and tested in COSMO model. During the COSMO User Seminar the latest results showing influence the revised parameterization
schemes for “bare soil” case on the structure atmospheric boundary layer will be shown.
Poster 11: High resolution simulations of the terrestrial carbon
flux using the Community Land Model (CLM) coupled to
COSMO
Dominik Brunner(1), Stephan Henne(1), Stefanos Mystakidis(2), Edouard L.
Davin(2), Christoph Gerbig(3)
(1) Laboratory for Air Pollution/Environmental Technology, Empa, Dübendorf, Switzerland,
(2) Institute for Atmospheric and Climate Science, ETH, Zürich, Switzerland,
(3) Max Planck Institute for Biogeochemistry, Jena, Germany
The largest uncertainty of our current understanding of the global carbon cycle lies within
the role of the terrestrial biosphere. Uptake and release of carbon dioxide (CO2 ) from and to the
atmosphere by photosynthesis and respiration, respectively, are sensitive to a large number of
environmental and physiological factors. Terrestrial biogeochemistry models (TBMs) that simulate the aforementioned processes in detail are utilised in global to regional scale climate models,
but their resolution often remains too coarse to be evaluated against atmospheric observations
and within atmospheric flux inversions on the meso-β and meso-γ scale and in heterogeneous
environments such as encountered in most of western and central Europe.
Here we present a newly derived, high resolution (kilometre scale) dataset of external parameters for the use with NCAR’s Community Land Model version 4 (CLM4.0) and evaluate its
performance when coupled to COSMO. The external parameter dataset comprises per-gridcell
percentages of land units (as used in CLM4.0: vegetated, urban, lake, glacier, wetland) and
plant functional types (16 vegetation classes), soil texture and organic carbon content, maximal
fractional saturated area (as used by the hydrological module of CLM4.0), and monthly vegetation parameters (leaf and stem area index, vegetation height) at a spatial resolution of 0.01◦ by
0.01◦ for the larger Alpine area as covered by the operational COSMO2 domain of MeteoSwiss.
47
Terrestrial carbon and nitrogen interactions are considered by activating the carbon and nitrogen module (C/N) in CLM4.0. The carbon and nitrogen pools in soils and vegetation were
brought at equilibrium by running CLM4.0 offline for ca. 600 years forced by a mean climatology of COSMO-CLM2 at 0.5◦ resolution. After spin-up a coupled COSMO-CLM simulation was
run for the year 2013 providing time resolved CO2 surface fluxes, separately for gross primary
production, ecosystem respiration and net ecosystem exchange. CLM simulated CO2 fluxes are
further compared to those obtained from the satellite based Vegetation Photosynthesis and Respiration Model (VPRM) estimates for the same parameters, period and area. The dataset will
also be of interest for high-resolution weather and climate simulations using CLM as land surface
model coupled to COSMO.
Poster 46: Development Version (DV) release of TERRA_URB
in COSMO(-CLM), overview and sensitivity to urban input
parameters
Hendrik Wouters(1), Matthias Demuzere(1), Ulrich Blahak(2), Gianluca Mussetti
(3, 4), Nicole van Lipzig(1), Jurgen Helmert(2), Matthias Raschendorfer(2),
Jan-Peter Schulz(2)
(1) Dept. Earth and Environmental Sciences, KU Leuven, Belgium,
(2) Deutscher Wetterdienst, Germany,
(3) Laboratory for Air Pollution/Environmental Technology, Empa, Switzerland,
(4) Laboratory for Multiscale Studies in Building Physics, Empa, Switzerland
TERRA_URB introduces an urban land-cover parametrization for the atmospheric system
COSMO-(CLM) and allows for the representation of cities in both the COSMO consortium as
well as the CLM community. TERRA_URB has been evaluated extensively for many European cities both in offline (Basel, Toulouse) and in online mode (Belgium, Berlin and Zürich).
It is also being used in several climate downscaling and urban-climate research projects such
as MACCBET (Modelling Atmospheric Composition and Climate for the Belgian Territory),
UPIM (Urban Precipitation Interaction Experiment) and CORDEX.be (COmbining Regional
Downscaling EXpertise in Belgium: CORDEX and Beyond). In addition, it has been used for
acquiring future urban heat-stress scenarios for Belgium published in the Climate Report 2015
of the Flemish Environmental Agency. As TERRA_URB is found reliable and efficient at the
same time, it has been accepted for implementation into the official COSMO code. With the
recent release of the Development Version (DV) of TERRA_URB, additional urban input fields
ISA (Impervious Surface Area) and AHF (Anthropogenic Heat Flux) have been introduced in
the latest version of EXTPAR (version 3.0). The development release of TERRA_URB also
introduces several advancements. They include the applicability of the TKE-based surface-layer
transfer scheme of COSMO and the introduction of the common urban morphological parameters
(the building height, street-canyon height-to-width ratio and roof fraction).
A model sensitivity experiment with COSMO-CLM coupled to TERRA_URB is performed
over Belgium during summer 2012. Hereby, each of the uncertain urban input parameters –
including the newly introduced urban morphology parameters above, the albedo, the specific
heat and conductivity of the buildings and streets, and the anthropogenic heat emissions – are
48
modified to the minimum and maximum values of the ranges of the so-called ’local climate
zones’ (Stewart and Oke, 2012). This way, the urban parameters are identified for which
urban regional climate modelling performance is the most sensitive. Based on this sensitivity
study, the weather forecasting and regional climate community can assign a higher priority to
the most sensitive urban parameters in their task of extending their global land-surface datasets.
Reference:
Stewart, I. D. and T. R. Oke, 2012: Local Climate Zones for Urban Temperature Studies.
Bulletin of the American Meteorological Society, 93 (12), 1879–1900, doi:10.1175/BAMS-D-1100019.1.
POSTER: Verification (NWP) and
Evaluation (RCM)
Poster 21: Estimating the downscaling ability of nested
RegCMv.4.3 with the GCM-ECHAM4.5 monthly forecast
ensembles as Boundary Conditions: Part I
Armenia Franco-Díaz(1), Ernesto Caetano(2), Clemente López-Bravo(1)
(1) National Autonomous University of Mexico (UNAM) Earth Sciences Postgraduate
Program,
(2) Institute of Geography (UNAM)
High-Resolution Regional Climate Models (RCM) have been used to downscale Global Climate Model (GCM) forecast data to produce high-resolution seasonal forecasts, successfully
producing several features of observed regional climates over various regions of the globe. Even
when downscaled simulations are assumed to have a certain satisfactory level for predicting
planetary and large-scale seasonal meteorological fields, and are believed to more accurate perform the regional climate details than GCMs, it’s mandatory to evaluate which RCM simulation
features related with mesoscale circulations patterns are better performed after applying the dynamical downscaling technique, and which large-scale features that come from GCM’s outputs
are maintained, in order to know the accuracy of the RCM to simulate the global circulations.
Investigating these issues might help us to clarify which is the added value that RCM provides
to the GCM’s forecast outputs, as a way to identify errors and biases that the RCM might have.
As a part of a Master’s thesis, this work presents a study case where is evaluated the performance of the RCM ICTP-RegCMv.4.3 nested atmospheric data simulated by the GCM IRIECHAM4.5 ensemble forecast, in forecasting boreal summer large scale circulation patterns over
an area that includes the tropical eastern Pacific Ocean and the tropical Atlantic Ocean. A twodimensional discrete spatial filter was used in both RegCM monthly mean input and output
fields, as a way to classify meteorological fields on a limited-area grid according to their spatial
dimension by filtering certain wavenumber ranges, i.e. for extracting mesoscale and large-scale
49
features from the atmospheric fields, and for regional validation. This way, high and low-pass input and output wind and moisture RegCM monthly mean fields are obtained and are compared
between them, as a means of identifying the added value of RCM forecast and detecting possible errors in the predicted fields. Additionally, both input and output relative vorticity fields
(built from their zonal and meridional wind fields) are used to develop an analysis based on the
tracking statistics of African easterly wave (AEW) activity, an important part of the tropical
Atlantic climate.
The results show that the RCM does not accurately retain the large-scale circulations provided
by the GCM over the tropical latitudes of the area of study, and the differences between them
increase with the consecutive months from the forecast begins. Furthermore, the statistics of
AEW seasonal forecasted for both input and output have significant differences, where those
that are developed from RCM outputs are not consistent with climatological features showed
in other studies that use a similar tracking technique (e.g. Thorncroft and Hodges, 2001). Since
has been suggested that the mesoscale dynamics might be widely conditioned by large-scale
variability and orographic regional detail, inconsistencies between the input and output largescale dynamics could affect significantly the RCM’s meteorological forecasted fields.
Poster 23: Feature-based methods application to COSMO PL
J. Linkowska, A. Wyszogrodzki
Institute of Meteorology and Water Management - National Research Institute, Warsaw,
Poland
In recent years the resolution of numerical weather prediction models has continued to increase
rapidly. Traditional verification scores such as the root-mean-square error, or those computed
form a contingency table, rely on an exact match between forecasts and observations in space
and time. They penalize even small differences in intensity and location of the verified features
and this "double penalty" effect becomes more pronounced when applied to a high or very high
resolution (convection-permitting) models.
In addition these traditional scores give no information about the structure or spatial location of the forecast errors. The application of spatial verification techniques gives a better
understanding of the forecast performance. The feature-based methods such as the Method for
Object-based Diagnostic Evaluation (MODE) and the Contiguous Rain Area (CRA), provide
information on errors in location, scale, intensity and structure in forecast fields.
COSMO PL 2.8 runs operationally at IMGW-PIB, the Polish National Weather Service. The
domain size covers the whole area of Poland and its close vicinities. Forecasts of 1h accumulated
precipitation have been verified against radar data using the MODE and CRA methods. This
presentation reports on the implemented verification methodology and shows the latest results.
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Poster 25: Mistral and Tramontane: Wind Patterns in Regional
Climate Simulations and Projections
A. Obermann, B. Ahrens
Goethe-Universität Frankfurt, Institut für Atmosphäre und Umwelt
The Mistral and Tramontane are mesoscale winds in the Mediterranean region that travel
through valleys in southern France. The cold and dry Mistral blows from the north to northwest,
and travels down the Rhône valley, between the Alps and Massif Central. The Tramontane
travels the Aude valley between the Massif Central and Pyrenees. Over the sea, these winds
cause deep-water generation, and thus impact the hydrological cycle of the Mediterranean Sea.
The occurrence and characteristics of Mistral and Tramontane depend on the synoptic situation, the channeling effects through mountain barriers, and land and sea surface characteristics.
We evaluate Mistral and Tramontane wind speed and direction patterns in COSMO-CLM and
other regional climate models from the MedCORDEX framework with respect to these challenges
for modeling.
Furthermore, time series of Mistral and Tramontane days events in historical and projection
runs are derived from sea level pressure patterns. The development of Mistral and Tramontane
days per year and the average length of such events is studied, as well as the development of
wind speeds.
Poster 27: Evaluation of the coupled
COSMO-CLM+NEMO-Nordic model with focus on North and
Baltic seas
J. Lenhardt, J. Brauch, B. Früh, T. van Pham
Deutscher Wetterdienst, Offenbach
The region east of the Baltic Sea has been identified as a hot-spot of climate change by Giorgi,
2006, on the base of temperature and precipitation variability. For this purpose, the atmosphere
model COSMO/CLM has been coupled to the ocean model NEMO, including the sea ice model
LIM, via the OASIS coupler (Pham et al., 2014).
Our aim is to find an optimal configuration of the already existing coupled regional
atmospheric-ocean model COSMO-CLM+NEMO-Nordic. So far results for the North- and Baltic
seas show that the coupled run has large biases compared with the E-OBS reference data. Therefore, additional simulation evaluations are planned by the use of independent satellite observation
data (e.g. Copernicus, EURO4M).
As COSMO-CLM and NEMO use different time steps, information between the models can
only be exchanged by specific time steps that fit both. Due to first analyzes it is presumed that
different coupling time steps have an impact on the results of the coupled model run. In order to
find the best configuration the coupled model have been run with different coupling time steps.
The results will be presented in this poster. Further tests are planned to understand whether
the lateral boundary conditions could influence the bias to observations.
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Poster 29: COPAT – towards a recommended model version of
COSMO-CLM
I.Anders(1), S. Brienen(2), E. Bucchignani(3), A. Ferrone(4), B. Geyer(5), K.
Keuler(6), D. Lüthi(7), M. Mertens(8), H.-J. Panitz(9), S. Saeed(10), J.P.
Schulz(2), H. Wouters(10)
(1) ZAMG- Central Institute of Meteorology and Geodynamics,
(2) DWD - Deutscher Wetterdienst,
(3) CMCC,
(4) LIST - Luxembourg Institute of Science and Technology,
(5) Helmholtz-Zentrum Geesthacht,
(6) BTU - Brandenburg University of Technology Cottbus,
(7) ETHZ - Federal Institute of Technology of Zurich
(8) DLR - Deutsches Zentrum für Luft- und Raumfahrt,
(9) KIT - Karlsruhe Institute of Technology,
(10) KU Leuven
The regional climate model COSMO-CLM is a community model (www.clm-community.com).
In close collaboration with the COSMO-consortium the model is further developed by the community members for climate applications. One of the tasks of the community is to give a recommendation on the model version and to evaluate the models performance.
The COPAT (Coordinated Parameter Testing) is a voluntary community effort to allow different institutions to carry out model simulations systematically by different institutions in order
to test new model options and to find a satisfactory model setup for hydrostatic climate simulations over Europe. We will present the COPAT method used to achieve the latest recommended
model version of COSMO-CLM (COSMO5.0_clm6).
The simulations cover the EURO-CORDEX domain at two spatial resolutions 0.44◦ and 0.11◦ .
They used ERAinterim forcing data for the time period of 1979-2000. Interpolated forcing data
has been prepared once to ensure that all participating groups used identical forcing. The evaluation of each individual run has been performed for the time period 1981-2000 by using ETOOL
and ETOOL-VIS. These tools have been developed within the community to evaluate standard
COSMO-CLM output in comparison to observations provided by EOBS and CRU.
COPAT was structured in three phases. In Phase 1 all participating institutions performed a
reference run on their individual computing platforms and tested the influence of single model
options on the results afterwards. Derived from the results of Phase 1 the most promising
options were used in combinations in the second phase (Phase 2). These first two phases of
COPAT consist of more than 100 simulations with a spatial resolution of 0.44◦ . Based on the
best setup identified in Phase 2 a calibration of eight tuning parameters has been carried out
following Bellbrat et al. (2012) in Phase 3. A final simulation with the calibrated parameters
has been set up at a higher resolution of 0.11◦ . The results were compared to previous model
versions. The new model version led to the same or better results and therefore had been defined
as the new recommended model version of the community.
Reference
Bellprat, O., S. Kotlarski, D. Lüthi, and C. Schär (2012), Objective calibration of regional
climate models,J. Geophys. Res., 117, D23115, doi:10.1029/2012JD018262.
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Poster 31: Elevation-dependency of the representation of
precipitation with COSMO-CLM 5.0 at 3km over the Alps.
Marie Piazza, Heimo Truhetz, Andras Csaki
Wegener Center for Climate and Global Change, University of Graz, Graz, Austria
Previous studies have shown that convection-permitting simulations accurately reproduce the
diurnal cycle of precipitation, especially over mountainous regions in summer. However, a strong
dependency to elevation has been shown with COSMO-CLM 5.0 at 3km. Indeed, the model is
unable reproduce the mid-afternoon peak in low- and flat-lands in the Eastern Alps.
Associated processes are investigated in the framework of NHCM-2 (project number P24758N29), using a set of sensitivity experiments over the greater Alpine region. These experiments
are designed to cover a broad range of influences, including orographic forcing and physical
parametrizations. Model evaluation is performed with a set of observations-based high-resolution
and high-quality datasets over the Eastern Alps. These datasets are provided by the Austrian
Central Department for Meteorology and Geodynamics (ZAMG), and high spatially and temporally resolved data from the nowcasting system INCA, and newly generated gridded datasets
from homogeneized high density network of in situ measurement stations. First results of processoriented analysis will be presented and discussed in the context of model intercomparison (including WRF).
Poster 33: Intercomparison of Spatial Verification Methods for
COSMO Terrain (INSPECT): Preliminary results
Alferov D. (1), Astakhova E. (1), Boukouvala D. (2), Bundel A. (1), Damrath U.
(3), Eckert P. (4), Gofa F. (2), Kirsanov A. (1), Lapillonne X. (4), Linkowska J.
(5), Marsigli C. (6), Montani A. (6), Muraviev A. (1), Oberto E. (7), Tesini M.S.
(6), Vela N. (7), Wyszogrodzki A. (5), Zaichenko M. (1)
(!) RHM,
(2) HNMS,
(3) DWD,
(4) MCH,
(5) IMGW-PIB,
(6) ARPA-SIMC,
(7) ARPA-PT
The COSMO consortium project devoted to spatial verification methods (INSPECT) targets
participation in MesoVICT activities (Mesoscale Verification Intercomparison over Complex Terrain) through the application of verification methods to the high and very high resolution models
(deterministic and EPS) comprising COSMO forecast systems. As such, the heart of INSPECT
involves analysis of data from the MesoVICT test cases (http://www.ral.ucar.edu/projects/icp/)
enabling comparison of different spatial methods and the creation of guidelines regarding the
applicability of each method. In addition to evaluating the accuracy of different methods on
53
the common test cases, the INSPECT project also targeted the creation of routines for data
pre-processing and for application of the most widespread spatial methods.
Preliminary results have been obtained and include: a. Comparison of traditional precipitation
scores and extreme event scores for the MesoVICT core case (HNMS) b. Application of the DIST
spatial method to the core case using different windows sizes (ARPA-SIMC), b. Exploration of
feature-based methods as CRA (Contiguous Rain Area) and MODE (Method for Object-based
Diagnostic Evaluation) (IMGW-PIB, Roshydromet) using R SpatialVx package. c. Analysis of
long time series of neighborhood scores (DWD) and neighborhood score aggregation based on
lead time (MCH).
Poster 35: Evaluating CLM and RegCM in Simulating Major
characteristcs of West Africa Climate
Abdoulaye Sarr
ANACIM
In this study, we intercompare CLM and regCM over West Africa. Models are assessed in
various key aspects of the climate of West AFrica with a main focus on Sahel region. A full
invistigation including climate indices and known drivers of the West Africa climate is carried
out.
Poster 37: Results of statistical correction of air temperature
forecasts for Siberian territory based on the COSMO-Ru_Sib
model
Zdereva M., Khluchina N., Voronina L.
Siberian Research Hydrometeorological Institute
Forecasts are calculated in the Siberian Computing Centre since 2012. Currently, the grid
spacing of the output forecast product is about 13 km. The assessment of near-surface air temperature forecasts is presented, and their spatial distribution and daily and seasonal variations
are shown. In the summertime, a simple statistical correction based on linear regression coefficients between the forecast and the actual temperatures within a limited moving sample can
significantly reduce bias and improve the accuracy of weather forecasts. In the cold period, the
correction requires the prior separation of weather situations.
54
POSTER: Predictability and
Ensemble Systems
Poster 32: Influence of orography on predictability using the
idealized COSMO-KENDA forecasting system
K. Bachmann(1), H. Lange(1), C. Keil(2)
(1) Hans-Ertel-Zentrum für Wetterforschung (HErZ),
(2) Meteorologisches Institut, LMU München (MIM)
The predictability of the weather is influenced by the interaction between synoptic forcing
and local-scale flow characteristics. Understanding of the forcing of moist convection impacts
the limits of predictability. The predictability timescale is lengthened in the presence of weak
atmospheric instability or stronger surface forcing. Particularly, the presence of orography can
serve as a trigger for convective precipitation under weak synoptic forcing thus enhancing its
predictability.
The idealized COSMO-KENDA test bed is used to investigate the influence of orography on
the predictability of precipitation. Following Lange&Craig(2014) convective-scale data assimilation of simulated Doppler radar observation is conducted in the presence of orographic forcing.
In a first step, the ensemble forecast quality is evaluated under the assumption of a perfect
model.
Poster 34: Ensemble Prediction System at IMWM-NRI Operational Setup and Preliminary Results of a Study in the
Frame of SPRED Priority Project
Andrzej Mazur, Grzegorz Duniec, Witold Interewicz, Andrzej Wyszogrodzki
Institute of Meteorology and Water Management - National Research Institute
Perturbations of the lower boundary state (i.e. layers of soil and the boundary between soil
and lower atmosphere) applied to Ensemble Prediction System(s) are believed to play an important role in preparing a valid set of ensemble members. As a part of COTEKINO (COSMO
Towards Ensembles at the Km-scale In Our Countries) priority project of COSMO (Consortium
for Small-scale Modelling) at the Institute of Meteorology and Water Management – National
Research Institute (IMWM-NRI) a simple method was proposed to produce a valid ensemble
member(s) ensemble, taking into consideration predefined soil-related model parameters. All
tests and experiments resulted in preparing a well-defined ensemble based on the perturbation
of soil-related perturbation, introduced in the COSMO model operational work at the IMWM NRI. First part of this study presents an operational set-up and examples of results. Yet, some
new main issues lead to the proposal of a new project in this field, called SPRED (Studying
Perturbations for the Representation of modelling uncertainties in Ensemble Development). The
55
stimulus was the need of improving the spread-skill relation of ensembles for surface weather
parameters. Newly picked, very preliminary results are presented in this work, concerning mentioned above the spread-skill relation statistically assessed for measurements carried out at Polish
meteorological stations.
Poster 36: Impact and perturbation growth of physical stochastic
boundary layer perturbations
Stephan Rasp, Kirstin Kober, George Craig
Meteorologisches Institut, Ludwig-Maximilians-Universität,München
The recently introduced stochastic boundary layer perturbation scheme aims at representing
small-scale variability due to unresolved physical processes. This basic version of the scheme
represents variability in convective boundary layer due to turbulence driven by surface heating. Therefore, it uses information from the model’s subgrid turbulence parameterization. The
stochastic perturbations lead to triggering of additional convective cells and improved precipitation amounts in situations of weak large scale forcing.
In this presentation, the impact of the perturbations will be further investigated using several
precipitation-based quality measures, such as the fractions skill score, in comparison to uncorrelated initial perturbations. The stochastic boundary layer perturbations lead to a significantly
faster displacement of cells compared to the uncorrelated perturbations adding spread to an
ensemble.
Furthermore, the upscale growth of the perturbations is analyzed following previous error
growth experiments. Measures, such as the difference total energy and the spectrum of kinetic
energy, are used to show that the boundary layer perturbations exhibit different growth characteristics compared to single, uncorrelated perturbations. This indicates that the variability in
the boundary layer represents a significant uncertainty, even for larger scales.
56
POSTER: NWP Model Applications
and Case Studies
Poster 41: Improved Understanding of an Extreme Rainfall Event
at the Himalayan Foothills
P. Shrestha(1), A. P. Dimri(2), A. Schomburg(3), C. Simmer(1)
(1) MIUB,
(2) Jawaharlal Nehru University,
In recent years, an increased occurrence of loss and damage of property and human casualties
over the southern rim area of the Himalayas, caused by landslides following intense rainfall
events, has been reported. An analysis of Tropical Rainfall Measuring Mission (TRMM)-gridded
rainfall data shows that events with an exceedance probability of 1.6 % for 200 mm/d rainfall
are common over this region during the monsoon season. An improved understanding of the
mechanisms, which lead to such events, is therefore important for their prediction and to estimate
the impact of climate change on their recurrence. In this study, we analyse such an extreme
precipitation event, which hit the Uttarakhand state in India on 13 September 2012. We use
the regional weather forecast model COSMO at a convection-permitting resolution of 2.8 km to
simulate this event and report on the mecahnism leading to such an event.
Poster 43: Two-way coupled simulations over Africa: How does
the feedback of the smaller scales alter the larger scales?
C. Hofmann(1), A, Kerkweg(1), P. Jöckel(2)
(1) Institute for Atmospheric Physics, University of Mainz, Germany,
(2) DLR, Institute for Physics of the Atmosphere, Oberpfaffenhofen, Germany
Within the BMBF-project MiKlip a two-way coupling between the global model EMAC
(ECHAM5/MESSy for Atmospheric Chemistry) and an arbitrary number of COSMO/MESSy
instances has been developed in the subproject FLAGSHIP (Feedback of a Limited-Area model
to the Global Scale implemented for HIndcasts and Predictions). This implementation of the
two-way coupling is based on the well established one-way on-line coupling system MECO(n)
(MESSyfied ECHAM and COSMO models nested n-times).
This newly developed two-way nested system is applied to investigate, if the feedback of
smaller scales to a larger scale can essentially alter the results in the coarser model instance. To
answer this question, we focus on the Sahara/Sahel region driven by the West African Monsoon.
This region is well known for its influence on the cyclogenesis over the Atlantic Ocean.
In prior studies it has been shown, that the intensification of tropical cyclones to hurricanes
takes only place in smaller scale models (in our test simulations in 0.22◦ , but not in 0.44◦
57
resolution). It has been demonstrated that in a two-way coupling setup the fate of the smaller
scale instance depends on the coupling setup. Since these statements are based on one thoroughly
tested case, more hurricane developments have been analysed to assess whether the feedback
from smaller scales generally improves the representation of hurricanes on larger scales.
Furthermore, the feedback due to two-way coupling of the scalar variables is analysed. In
particular, a dust outbreak over West-Africa and its feedbacks to the global scale dependent on
different model setups are evaluated.
Poster 45: Model assessment of small-scale water vapour
variability across spatial scales during heavy precipitation events
in the western Mediterranean.
A. Caldas-Álvarez, S. Khodayar
Institute of Meteorology and Climate Research (IMK-TRO), Karlsruhe Institute of Technology
(KIT).
During autumn, the western Mediterranean is prone to heavy precipitation and devastating
floods, mainly caused by Mesoscale Convective Systems (MCS). The strength and danger of such
events can be seen in documented past cases where casualties and millionaire losses are reported.
In order to better predict these extreme events further research is needed to investigate the
complex interactions between humidity and convection, which are still poorly understood. This
mutual influence can be observed, for instance, in the initiation of convection where atmospheric
moisture affects the instability of the lower air masses.
The main objective of this research work is to assess how well the COSMO model represents
the interaction between atmospheric humidity and convection across spatial scales.
COSMO runs with three different grid spacings (7 km, 2.8 km and 500 m) are investigated
during selected Intensive Observation Periods (IOPs) that occurred during the HYdrological
cycle in the Mediterranean EXperiment (HyMeX). The HyMeX experiment took place during
the early autumn of 2012 in the western Mediterranean region. The observational data sets that
are used to validate our model results are obtained from the dense network of HyMeX. A special
focus is put on the HyMeX GPS-derived Integrated Water Vapour (IWV), given that it has been
especially homogenized for HyMeX over the western Mediterranean region and offers a temporal
resolution up to 5 minutes.
58
Poster 47: The choice of the variographical model for Kriging
interpolation of data of pressure, temperature and precipitation
of model COSMO
L. Katsalova, V. Shpyg
Ukrainian Hydrometeorological Institute
Using mathematical models have long entered the world practice of the weather forecasting.
However, in the world there are not many models that describe the processes occurring in the
atmosphere and give weather forecast (GFS, ICON, WRF et al). A significant development in
recent years reached COSMO model. Ukraine, like most countries, uses data of such models in
operational practice and for research. Particularly, WRF and COSMO models are run for these
aims in the Ukrainian Hydrometeorological Institute.
For using of the model it’s necessary to conduct its verification, compare forecast with observation data. Interpolation of values of the meteorological parameters from domain grid of model
into the irregular grid of the Ukrainian meteorological stations carried out with this purpose.
One from the spread method of interpolation is Kriging (Kanevskiy et al.,1999). It optimizes of
interpolation procedure on the base of statistical nature of surface. The value of error of Kriging
consists of input data error, computing error and error of the method. Kriging method is based
on the assumption of unbiased estimate and minimization of variance (Katsalova and Shpyg,
2014a). This makes it possible to obtain the optimal interpolation on the condition of the exact
variogram. That is, than more accurately variogram describes the distribution of input data, the
smaller the error of interpolation.
The choice of variographical model, so called variography, for Kriging-interpolation of COSMO
model forecast data of MSLP, air temperature (2 m) and precipitation is conducted among
following theoretical models: linear, exponential, gauss, spherical, quadratic, nagget-effect, cubic,
logarithmical, power law model, circle model (Katsalova and Shpyg, 2014b).
Numerical experiments shown that than less RMSE between values of the theoretical model
and experimental variogram, the less RMSE of the Kriging-interpolation. Corresponding to this,
the conception of the optimal and quasi-optimal variographical models are proposed. Optimal
model from among models, that are referred above, is model in which RMSE is minimal. The
model is quasi-optimal if its RMSE belongs to the interval [RMSEopt, RMSEopt + c*RMSEopt).
Where value c is different for MSLP, temperature and precipitation and it is found by numerical
experiment for the following considerations: let f(x) = ax+b – linear function, that describe
dependence of RMSE of Kriging-interpolation from RMSE of variography, then c = (f(xmax)b)/(a* xmax)-1. In practicular, for temperature, c = 0.3◦ C.
Optimal and quasi-optimal models for MSLP, temperature and precipitation on datasets of
forecast of model COSMO for April 2013 - March 2014 are determined. Obtained results are base
for Kriging-interpolation of forecast of COSMO into the grid of the Ukrainian meteorological
stations in quasi-operational mode.
References
Kanevskiy M.F., Demyanov V.V., Savelyev E.A., Chernov S.Y. and V.A. Timonin, 1999:
An elementary introduction to geo statics. VINITI. Series "Problems of the Environment and
Natural Resources", Moscow. 11. 135 p.
Katsalova, L.M., and V.M. Shpyg 2014a: Application of Kriging-Interpolation for COSMO
Weather Forecast. COSMO/CLM/ART User Seminar: 17-19 March
59
Katsalova, L.M., and V.M. Shpyg, 2014b: Variographic Models of Meteorological Parameters
distribution on the territory of Ukraine for Kriging-interpolation (in Ukrainian). Scientific papers
of UHMI, 266, 20-26.
Poster 2: High-resolution climate change simulations for West
Africa with CCLM and WRF
Diarra Dieng(1, 2), Dominikus Heinzeller(1), Jan Bliefernicht(2), Gerhard
Smiatek(1)and Harald Kunstmann (1, 2)
(1) Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research
(IMK-IFU),
(2) University of Augsburg, Chair for Regional Climate and Hydrology
The climate change modeling activities within the WASCAL program (West African Science
Service Center on Climate Change and Adapted Land Use) concentrate on the provisioning
of future climate change scenario data at high spatial and temporal resolution. Such data is
required for subsequent impact studies and for the development of adaptation and mitigation
strategies. Within WASCAL, the regional climate models CCLM and WRF are applied over
West Africa in a nested approach with two simulation domains at 0.44◦ and 0.11◦ . In this
contribution, we describe in broad terms the international WASCAL program and present in
detail an evaluation and analysis of the performed model runs. To account for the uncertainty in
global climate projections that are used as lateral boundary conditions, we adopt an ensemble
approach with forcing data provided by MPI-ESM, GFDL-ESM2M and HadGEM2-ES. Here,
we describe the setup of the models and present first results for the historical period from 1980
to 2010 and for two future periods from 2020 to 2050 and 2070 to 2100, respectively. Special
attention is paid to the reproduction of the dynamics of the West African Monsoon (WMA)
and its associated precipitation patterns. Our contribution focuses on five investigation areas,
reflecting the different climatic characteristics in the region between the Guinea Coast and the
Sahel Zone.
60
Poster 4: Evaluation of COSMO-CLM for seasonal simulations
over Brazil
Reinaldo Silveira
Instituto Tecnologico SIMEPAR
The COSMO-CLM model has been tested for seasonal and climate prediction applications for
Brazil. For seasonal simulations, the driven global model is the CPTEC/COLA GCM, which is
spectral with resolution T62L28. This corresponds to triangular truncation of 62 waves in the
horizontal coordinate and 28 levels in the vertical sigma coordinate (21 in the troposphere and 7
in the stratosphere). Deep cloud convection and other physical processes, such as the soil/surface
interaction with atmosphere and radiative processes, are parameterized and the initial conditions
for the model are obtained from NCEP. Adaptations on the original data format were needed
for nesting two domains for COSMO-CLM: a large one covering Brazil and South America, with
horizontal grid spacing of 25km, and another for the South region of Brazil with 7km mesh size.
Three 4-month periods were simulated and compared to observations and NCEP reanalysis data,
as well as to climatological parameters; either for selected points or for areal averaging. Despite
underestimation of rainfall over continental portion, the results so far indicate that the COSMOCLM simulates closely to the GCM and observational climatology, with noticeable refinement
of the regional simulation of the predicted variables, such as the 2-m temperature.
Poster 6: Climate Modeling over the Mediterranean Sea: Impact
of Resolution and Ocean Coupling
Naveed Akhtar(1), Jennifer Brauch(2), Bodo Ahrens(1)
(1) IAU, Goethe University, Frankfurt am Main, Germany,
(2) Deutscher Wetterdienst, Offenbach am Main, Germany
The feedbacks between the Mediterranean Sea and the atmosphere on top at various temporal
and spatial scales play an important role in the regional climate system by modifying the air-sea
fluxes. A regional climate model COSMO-CLM with 9̃ km and 5̃0 km horizontal grid spacings
in atmosphere-only and coupled, with the ocean component NEMO-MED12, configuration is
employed to study the impact of horizontal atmospheric grid resolution and ocean coupling
on air-sea fluxes of heat and wind speed on seasonal and annual timescales. Furthermore, the
impact of diurnal variations of sea surface temperature simulated by the atmosphere-ocean
coupled model on air-sea fluxes of heat and wind speed is analyzed on sub-daily timescale. The
results show that the estimates of air-sea fluxes of heat are largely and wind speed is moderately
improved through ocean coupling. However, the wind speed is considerably improved with finer
atmospheric grid simulations especially around the coastal areas. The finer atmospheric grid
resolution moderately improves the seasonal mean of air-sea fluxes of heat in some areas of the
Mediterranean with minor impact on the basin-averaged. The air-sea fluxes of heat are largely
improved by the ocean coupling and wind speed by finer atmospheric grid resolution. Temporally,
the winter and autumn seasons and spatially, north and western parts of the Mediterranean Sea
are more sensitive to the ocean coupling and finer atmospheric grid resolution. The results
61
suggest that ocean coupling and finer atmospheric grid resolution improve the simulation of
the regional climate system in representing the air-sea fluxes over the Mediterranean Sea. The
sensitivity experiment shows that sea surface temperature diurnal variations strongly modify
the sub-daily air-sea fluxes, but are of minor relevance at longer timescales in the investigated
parameters over the Mediterranean Sea.
Poster 8: Deep Convection over Corsica: Influence of
Atmosphere-Ocean Interactions
Nora Leps, Erwan Brisson, Naveed Akhtar, Bodo Ahrens
Institute for Atmospheric and Environmental Sciences
The Mediterranean Region (MR) is a climate change hotspot and the future development
of extreme events is not well simulated. In the MR, due to favourable conditions especially in
autumn, near-coastal atmospheric deep convection (DC) often occurs and can be the cause of
hazardous heavy precipitation events and flash floods. Here we analyse how the interactions
between ocean surface and atmosphere due to diurnal variations in sea surface temperature
influence the DC in coastal mountain ranges (more precisely over the island of Corsica) via the
connection of local wind systems. To that end, convection permitting simulations with COSMOCLM on a regional domain over several days are performed.
To assess the influence of atmosphere-ocean interactions, simulations with CCLM and ERAInterim initial and boundary data, while sea surface temperature boundary data is in some cases
taken from NEMO, driven by ERA-Interim, and finally coupled atmosphere-ocean (CCLM and
NEMO) simulations are carried out.
The high resolution (ca 2.8 km) simulations represent small scale processes, however surface
fluxes and thus wind and moisture transport are strongly differing with the different representations of the diurnal sea surface temperature cycle.
62
Poster 10: On the role of the Alps for Central European Climate
Curdin Spirig, Daniel Lüthi, Christoph Schär
Institute for Atmospheric and Climate Science, ETH Zurich
Orography has a strong influence on weather and climate. Large mountain ranges affect the
global circulation and determine the distribution of different climate regimes. Being a smaller
mountain range in Central Europe, the Alps might not have a strong influence on the global
scale. However, for Central European weather and climate the orographic effects of the Alps
are crucial. Different synoptic and mesoscale flow phenomena such as lee-cyclogenesis or Föhn
are related to these mountains. Moreover Alpine orography is responsible for the distribution
of temperature and precipitation both over the Alps as well as in the vicinity upstream and
downstream of the Alps.
The orographic effects of the Alps on the European climate are investigated and quantified
using two simulations of the regional climate model COSMO-CLM at a resolution of 12 km .
The model domain and configuration are identical to what was used in the EURO-CORDEX
evaluation experiments with the difference that the new recommended version of the CLMcommunity was used (i.e. COSMO5.0_clm6). Simulations are integrated over a 32 year period
(1979-2010) with ERA-Interim data as initial data and boundary forcing. The control simulation
uses realistic Alpine topography. In the no-alps experiment the Alpine topography is shrunk and
several surface parameters are adjusted accordingly.
A comparison of the resulting climates of the two experiments shows the response of the
European climate to the presence of the Alps.
Poster 13: Modeling of the extreme winds over the Russian
Arctic basin using different COSMO-CLM model resolutions.
V. Platonov, A. Kislov
Lomonosov Moscow State University, Faculty of Geography, Department of Meteorology and
Climatology
Simulation and prediction of severe weather events including extreme winds is very important
and actual problem. These events have many dangerous consequences for navigation, coastal
ports infrastructure, oil-and-gas marine platforms and environment in the Arctic basin. Extreme
winds are closely connected with many mesoscale processes and its interactions with synopticscale circulations; therefore, its fine resolving and investigation is determined and possible by
high-resolution atmospheric modeling only.
The COSMO-CLM model was used for many case-studies simulation of the most extreme
winds observed over the Russian Arctic basin during the last 15 years. These extreme cases were
sorted out previously from observations samples, based on the 0.99 quantiles of Weibull and
Pareto distributions, i.e. the wind speed exceeded 20 – 25 m/s.
Model runs were performed as for the unified ‘large’ domain with spatial resolution of 1̃5 km,
as for the different ‘small’ domains (resolution of 2̃ – 3 km), using the downscaling technology.
These domains cover Barents Sea, part of Kara Sea and the surrounding water areas. Driving
63
conditions came from ERA-Interim reanalysis (0̃.750). Standard configuration of COSMO-CLM
5th version was applied: Runge-Kutta integration scheme with 5th advection order; 50 vertical
levels; prognostic TKE-based scheme for turbulence; standard Tiedtke convection scheme. Runs
continued for a week for the most cases, with the extreme situations observed near the middle
period.
Experiments has shown the 15 km resolution model runs could underestimate the maximal
10 m wind velocity up to 4 – 5 m/s, but it reproduces different synoptic situations and spatial
distribution of wind speed and gusts well. However, after the downscaling to 2̃.8 km, the reproduction of mesoscale fields was significantly better according to extreme wind speeds and gusts.
The mean error and the root mean square error decreases to 2 – 3 m/s. The spatial distribution
of wind fields it these cases turns more detailed and complicate, it is affected by the land-sea
distribution, complex terrain and, perhaps, non-hydrostatic effects. Extreme coastal winds were
observed mainly when the close isobars are parallel to the coast, or it is intensifying dynamically
over the narrow sea belts (e.g., Kara Strait).
Future tasks are to search an optimal model configuration for this region, applicate it for the
extreme wind fields reproduction, and use many additional opportunities for adaptation (e.g.,
spectral nudging or other parametrizations). Besides, an attempt of the physical interpretation
of these severe events will be done.
Poster 15: Continuously on-going hindcast simulations for
impact applications
I. Anders(1), B. Geyer(2)
(1) ZAMG,
(2) Helmholtz-Zentrum Geesthacht
Observational for e.g. temperature, precipitation, radiation, or wind are often used as meteorological forcing for different impact models, like e.g. crop models, urban models, economic
models and energy system models. To assess a climate signal, the time period covered by the
observation is often too short, they have gaps in between, and are inhomogeneous over time, due
to changes in the measurements itself or in the near surrounding. Thus output from global and
regional climate models can close the gap and provide homogeneous and physically consistent
time series of meteorological parameters.
CORDEX evaluation runs performed for the IPCC-AR5 provide a good base for the regional
scale. However, with respect to climate services, continuously on-going hindcast simulations are
required for regularly updated applications.
In this study two projects are presented where hindcast-simulations optimized for a region of
interest are performed continuously.
The hindcast simulation performed by HZG covering Europe includes the EURO-CORDEX
domain with a wider extend to the north to cover the ice edge. The simulation under consideration of the coastDat-experiences is available for the period of 1979 – 2015, prolonged ongoing
and fulfil the customer’s needs with respect of output variables, levels, intervals and statistical
measures. CoastDat – customers are dealing e.g. with naval architecture, renewable energies,
offshore wind farming, shipping emissions, coastal flood risk and others. The evaluation of the
64
hindcast is done for Europe by using the EVAL-tool of the CCLM community and by comparison
with HYRAS - data for Germany and neighbouring countries.
The Climate Research group at the national Austrian weather service, ZAMG, is focusing
on high mountain regions and, especially on the Alps. The hindcast-simulation is forced by
ERA-interim and optimized for the Alpine Region. One of the main tasks is to capture strong
precipitation events which often occur during summer when low pressure systems develop over
the Golf of Genoa, moving to the North-East. This leads to floods and landslide events in Austria,
Czech Republic and Germany. Such events are not sufficiently represented in the CORDEXevaluation runs. ZAMG use high quality gridded precipitation and temperature data for the
Alpine Region (1-6km) to evaluate the model performance. Data is provided e.g. to hydrological
modellers (high water, low water), but also to assess icing capability of infrastructure.
Poster 17: To provide a high-quality convection-permitting
ensemble member for the Belgian climate change with
COSMO-CLM in the CORDEX.be project
Hendrik Wouters, Sam Vanden Broucke, Nicole van Lipzig, Matthias Demuzere
KU Leuven
Much expertise is present in Belgium concerning regional climate-modelling research which
is currently brought together in the CORDEX.be project “COmbining Regional Downscaling
EXpertise in Belgium: CORDEX and Beyond” of the Belgian Science Policy Office (BelSPo). In
this project, the different Belgian institutes use their various climate models and configurations
to perform coherent long-term regional climate simulations for the Belgian domain using a
resolution in the order of 2-4 km, thus creating a Belgian Convection-Permitting Model (CPM)
ensemble “CORDEX.be”. Hereby, KU Leuven contributes the downscaling of one of the 16 ECEARTH RCP8.5 members provided by the Royal Meteorological Institute of the Netherlands
(KNMI), and for which the member is selected with a ’mean climate-sensitivity’ analysis. The
downscaling is obtained with regional climate simulations at 2.8km resolution over Belgium using
COSMO-CLM coupled to urban land-surface parametrization TERRA_URB for the presentday (1976-2005) and future (2041 – 2070 and 2071 – 2100).
Recent research shows that high-resolution modelling resolving the convection-permitive scales
and the detailed orography and land-use including urbanization leads to better modelling performance with respect to temperatures and precipitation. Based on the regional climate simulations
described above, we address how climate-change statistics are modified when going from coarse
resolution modelling to high-resolution modelling. The climate-change statistics of interest are
the changes in number of extreme precipitation events and extreme heat waves in cities. We
further investigate the robustness of the signal change between the course and high-resolution
scale and whether a (statistical) translation is possible. It also sought for the relevance of the
urban heat island and urban expansion (relative to the increased green-house gases), and to
what extent they can be included in the translation.
65
Poster 19: High-resolution climate change simulations for West
Africa with CCLM and WRF
Diarra Dieng (1, 2), Dominikus Heinzeller(1), Jan Bliefernicht(2), Gerhard
Smiatek(1), Harald Kunstmann (1, 2)
(1) (KIT)Karlsruhe Institute of Technology (KIT), Germany,
(2) University of Augsburg, Chair for Regional Climate and Hydrology, Germany
The climate change modeling activities within the WASCAL program (West African Science
Service Center on Climate Change and Adapted Land Use) concentrate on the provisioning of
future climate change scenario data at high spatial and temporal resolution. Such data is required
for subsequent impact studies and for the development of adaptation and mitigation strategies.
Within WASCAL, the regional climate models CCLM and WRF are applied over West Africa
in a nested approach with two simulation domains at 0.44◦ and 0.11◦ . In this contribution, we
present in detail an evaluation and analysis of the performed model runs. To account for the
uncertainty in global climate projections that are used as lateral boundary conditions, we adopt
an ensemble approach with forcing data provided by MPI-ESM, GFDL-ESM2M and HadGEM2ES. Here, we describe the setup of the models and present first results for the historical period
from 1980 to 2010 and for two future periods from 2020 to 2050 and 2070 to 2100, respectively.
Special attention is paid to the reproduction of the dynamics of the West African Monsoon
(WMA) and its associated precipitation patterns. Our contribution focuses on five investigation
areas, reflecting the different climatic characteristics in the region between the Guinea Coast
and the Sahel Zone.

Book of Abstracts - CLM

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