K. Liechti and M. Zappa (WSL) L. Panziera and U. Germann

NORA Ensemble for Operational Hydrology
*
First results of coupling NORA with PREVAH
K. Liechti and M. Zappa (WSL)
L. Panziera and U. Germann (MeteoSwiss)
*Nowcasting Orographic Rainfall using Analogs
NORA: The NORA Ensemble originates from meteorological analogs of the current meteorological situation. An archive is searched
for past situations with the most similar mesoscale winds, air mass stability and Weather radar quantitative precipitation estimates
(QPE). The radar QPEs following these past analogs are the basis of the NORA ensemble.
Hydrological Model
PREVAH (Precipitation Runoff Evapotranspiration HRU related
model)
Input Parameters (hourly):
air temperature, water vapour pressure, global radiation, wind
speed, sunshine duration and precipitation from 3 different sources
(Viviroli et al. 2009).
The Verzasca river basin
The hydrographs (below)
Parameter Ensemble: The spread achieved by the parameter ensemble (Monte Carlo sampling) is minimal and follows to great parts
the deterministic RADAR and PLUVIO runs. The observation lies
mostly outside the ensemble spread. Neither the first nor the second
peak discharge (6./7. Sept.) could be detected with this setup.
Radar Ensemble (REAL): The 25 members of the Radar ensemble
develop some spread up to the point where it is coupled to COSMO-7
in order to do some forecast. Shortly after that the members converge
again. It is therefore not possible to detect the discharge peaks ahead.
NORA Ensemble: The NORA ensemble provides an 8 h Radar QPE
forecast after which it is coupled to the COSMO-7 forecast. In contrast
to the Parameter Ensemble and Radar Ensemble NORA captures the
tendency of a rising limb and the observed hydrograph is in the ensemble range.
The Verzasca river basin lies in the Southern Swiss Alps. Up to the
2
gauge in Lavertezzo it has an area of 186 km . It is little affected by
human activities. It is characterised by snow melt in spring and
early summer and heavy rainfall events in autumn.
PAR−ENS Cum.Precipitation Verzasca
WL3
200
50
0
0
Radar ENSEMBLE first try Verzasca
REAL Cum.Precipitation Verzasca
Median
MIN/MAX
IQR
REAL COSMO−7
250
300
REAL COSMO−7
200
150
200
WL2
100
Discharge gauge
RADAR det.
PLUVIO
NORA Persistence
NORA MEAN
REAL MIN/MAX
REAL IQR
WL3
precipitation [mm/h]
0
50
WL1
00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC
Di 02−Sep
Mi 03−Sep
Do 04−Sep
Fr 05−Sep
Sa 06−Sep
So 07−Sep
Mo 08−Sep
00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC
Di 02−Sep
Mi 03−Sep
Do 04−Sep
Fr 05−Sep
Sa 06−Sep
So 07−Sep
Mo 08−Sep
NORA ENSEMBLE first try Verzasca
NORA Cum.Precipitation Verzasca
300
NORA COSMO−7
Median
MIN/MAX
IQR
NORA Sequence
WL2
precipitation [mm/h]
Discharge gauge
RADAR
PLUVIO
NORA Persistence
NORA MEAN
NORA MIN/MAX
NORA IQR
WL3
0
WL1
0
100
100
init
200
500
00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC
Di 02−Sep
Mi 03−Sep
Do 04−Sep
Fr 05−Sep
Sa 06−Sep
So 07−Sep
Mo 08−Sep
300
400
00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC
Di 02−Sep
Mi 03−Sep
Do 04−Sep
Fr 05−Sep
Sa 06−Sep
So 07−Sep
Mo 08−Sep
0
500
400
150
precipitation [mm/h]
200
WL1
300
200
PAR−ENS COSMO−7
WL2
100
discharge [m3/s]
discharge [m3/s]
Median
MIN/MAX
IQR
250
300
PAR−ENS COSMO−7
300
Discharge gauge
RADAR det.
PLUVIO
NORA Persistence
NORA MEAN
PARENS MIN/MAX
PARENS IQR
100
discharge [m3/s]
400
500
Parameter ENSEMBLE first try Verzasca
100
a)
Cumulative Precipitation (below)
The Radar Ensemble gains its spread up to the point, where it is
coupled to the deterministic COSMO-7. At that time NORA is initialised and starts developing its spread. At the end of the NORA sequence there is more water in the system than in the cases above
(COSMO-7 forecasts too little rainfall), which in this case enlarges the
forecast probability of the first discharge peak (6. Sept.).
00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC
Di 02−Sep
Mi 03−Sep
Do 04−Sep
Fr 05−Sep
Sa 06−Sep
So 07−Sep
Mo 08−Sep
00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC 12 UTC 00 UTC
Di 02−Sep
Mi 03−Sep
Do 04−Sep
Fr 05−Sep
Sa 06−Sep
So 07−Sep
Mo 08−Sep
Parameter Ensemble
26 Members
26 model versions are run with
precipitation input obtained
from interpolated station data.
COSMO-7 precipitation forecasts are coupled to the nowcasts.
Radar Ensemble
25 Members
Perturbed versions of the current Radar QPE are given for
the next hour (Nowcast).
COSMO-7 precipitation forecasts are coupled to the nowcasts.
NORA Ensemble
12 Members
Deterministic Radar input up to
the initialisation of NORA.
NORA provides an 8 h forecast,
thereafter we switch to
COSMO-7 input.
NORA Persistence: Keeping the last available Radar QPE constant.
NORA MEAN: The mean out of 12 NORA members.
FP7-ENV-2008-1 IMPRINTS 226555