Session 1.4 (presentation)

Regional activities at Mercator Ocean:
toward a regional operational system
on the IBI domain
S. Cailleau, J. Chanut, B. Levier, G. Reffray
www.mercator-ocean.fr
Regional modelling at Mercator Ocean
Deliver by 2012 (My Ocean project) a
high resolution (2 km) regional
operational system over the IBIROOS
area (France, Ireland, Portugal, Spain):
“Façade” project
Ifremer
Expected: great improvement of
initial/boundary conditions provided to
coastal modelers
Developments in NEMO-OPA: tides,
runoff, advection schemes, vertical
physics, OBC, high resolution
atmospheric forcing, atmospheric
pressure, …
www.mercator-ocean.fr
Regional modelling at Mercator Ocean
How to validate these developments ?
Intercomparison project: identify
strengths and weaknesses of models
(HYCOM, NEMO-OPA, MARS,
MOHID, SYMPHONIE)
- improvements of models
- reinforce links between
teams
Intercomparison
Next step: EPIGRAM project
Façade
www.mercator-ocean.fr
Model Intercomparison in the Bay
of Biscay during 2004
G. Reffray, B. Levier (Mercator-Ocean): NEMO-OPA
P. Marsaleix (POC CNRS): SYMPHONIE
P. Lazure & V. Garnier (IFREMER): MARS3D
R. Baraille (SHOM): HYCOM
G. Riflet (IST, Portugal): MOHID
www.mercator-ocean.fr
Configuration
- bathymetry SHOM 1’
- grid’s resolution of 3 km
- MO North Atlantic system
PSY2v1 at the open boundaries
- atmospheric forcing with
ALADIN (Météo-France) at 3 h
- tidal forcing with MOG2D (9
components)
- daily runoff of 3 rivers
(Adour, Gironde, Loire)
- Year 2004
www.mercator-ocean.fr
Database
- Bay of Biscay climatology (F. Vandermeirsh, IFREMER)
0.4° on horizontal, 261 vertical levels
O buoys
X tidal gauges
- daily SST MODIS (4 km)
- time series: 8 buoys and 18 tidal gauges
- in-situ profiles from 2 oceanographic campaigns:
Pelgas (28/04/04 – 23/05/04), 75 profiles
Evhoe (29/10/04 – 12/12/04), 101 profiles
www.mercator-ocean.fr
PELGAS
EVHOE
Processes
Ushant’s front
And also:
- Internal waves
Thermal front
Upwelling
Warmpool
MODIS image in June
www.mercator-ocean.fr
- Cold pool
- Rivers plumes
Models characteristics
NEMO-OPA
SYMPHONIE
MARS
Free surface
Time-splitting
Linear free surface
Time-splitting
Time splitting ADI
(Lazure and Dumas, 2008)
Vertical
coordinate
Cartesian + partial-cells
49 levels
Generalized sigma
coordinates 43 levels
Sigma coordinates
40 levels
Scalar advection
QUICKEST + ULTIMATE
(Leonard, 1979, 1991)
Hybrid 2nd order center
and upwind
QUICK (Leonard, 1979)
Scalar horizontal
diffusion
-
-
Laplacian : 1m2s-1
Momentum
advection
Form vector conserving
energy and enstrophy
(Arakawa and Hsu, 1990)
Flux form 2nd order
center
Flux form QUICK
(Leonard, 1979)
Momentum
horizontal
diffusion
Biharmonic
-5.108m4s-1
Laplacian with velocity
depending coefficients
Laplacian
+ Smagorinsky (1963)
Vertical
diffusion
TKE + mixing length
(Blanke and Delecluse,
1993)
TKE + mixing length
(Gaspar et al., 1990)
TKE + mixing length
(Gaspar et al., 1990)
Surface
boundary
condition
Bulk formulae
(Large and Yeager, 2004)
Bulk formulae
(Large and Yeager, 2004)
Bulk formulae
(Gill, 1982)
www.mercator-ocean.fr
Harmonic analysis (1)
M2
amplitude
www.mercator-ocean.fr
MOG2D
OPA
SYMP
MARS
Harmonic analysis (2)
M4
amplitude
MOG2D
SYMP
www.mercator-ocean.fr
OPA
MARS
Internal waves
Hourly outputs along a section
FFT on SSH and on U at 3 depths for
September
M4
M2
M4
OPA
www.mercator-ocean.fr
M2
M4
SYMP
M2
MARS
Hydrology over the shelf
Comparison with EVHOE in-situ data
OPA
Temperature
MARS
SYMP
Salinity
OPA
www.mercator-ocean.fr
SYMP
MARS
Mixing (1)
Ushant’s front
Differents behaviour of the models on a particular day
MODIS
2004/07/06
www.mercator-ocean.fr
OPA
SYMP
MARS
Mixing (2)
MODIS
OPA
SYMP
Ushant’s front
Space-time diagram
of the SST
normalized by the
minimum of the
SST along a zonal
section across the
Ushant’s front
www.mercator-ocean.fr
MARS
Location of temp min
Minimum of temperature
Rivers plumes
Annual mean
of SSS
CLIM
SYMP
www.mercator-ocean.fr
OPA
MARS
Very small
extension with
OPA due to
“fixed volume”
Fresher water
can’t cross the
shelf-break of
the Landes
shelf with OPA
and MARS
Intercomparison summary
- similar results for all the models
- physical processes modelised close to observations
Improvements already implemented in NEMO-OPA:
- non-linear free surface (variable volume)
- tunning of the vertical mixing
⇒●Rivers plumes
●Tides
www.mercator-ocean.fr
Development of a high resolution model over
the North East Atlantic: “Façade” project
Mercator Ocean IBI regional
systems:
● 1/12° (6 km) grid (extracted from
global ORCA grid) Nested in 1/12°
North Atlantic
Data assimilation underway
● 1/36° (2 km) grid (My Ocean)
No data assimilation yet
www.mercator-ocean.fr
Tidal implementation (1)
M2 amplitude (m) and phase (degree)
FES2004
www.mercator-ocean.fr
NEATL36
Tidal implementation (2)
Complex amplitude error Hc (m) relative to FES2004 for M2
NEATL12
www.mercator-ocean.fr
NEATL36
Conclusion
2 years already performed
Future work essentially on the 1/36°:
- sensivity experiments
- validation needed
To be continued …
Reference:
Mercator Ocean Quaterly Newsletter #30, July 2008:
- Towards North East Atlantic Regional modelling at 1/12° and 1/36°
at Mercator Ocean
- Model intercomparison in the Bay of Biscay during 2004: the front
of Ushant and the cold water pool
www.mercator-ocean.fr