The Mercator experience

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www.mercator.eu.org
Data Assimilation and Operational
Oceanography:
The Mercator experience
Benoît Tranchant btranchant@mercator-ocean.fr
And the Mercator-Ocean Assimilation Team
(Marie Drevillon, Elisabeth Remy, Mounir Benkiran, Eric Greiner, Jean-Michel
Lellouche, Laurent Parent and Charles Emmanuel Testut)
NEMO users meeting 2006
Mercator Ocean: An OPA user
but also an OPA developer
OPA configurations used in operational (2006):
North Atlantic (OPA8.1/rigid lid)
MNATL medium (1/3°) and PAM high (1/15°) resolution
Global (OPA8.2/free surface)
ORCA2 and ORCA025
Next important steps:
Regional: 1/3° & 1/15°
•OPA-NEMO:
•ATL4, ORCA025 and ATL12 in 2007
•ORCA12 in 2008
Global: 2° & 1/4°
2006developer
Mercator Ocean: A DA user and
Brief overview of data assimilation schemes:
SAM1-v1: Univariate OI (SLA).
SAM1-v2: Multivariate OI (SLA, SST and T/S profiles)
Operational
using 1D vertical modes
R&D
SAM2-v1: Multivariate SEEK filter (SLA, SST HR and
T/S
profiles) using 3D modes
SAM3-v0: Multivariate 3D-Var (SLA and T/S profiles)
Mercator Data Assimilation Systems
: SAM
2006
OCEAN MODEL: OPA-NEMO
DATA ASSIMILATION SCHEMES
•SAM1 : OI
•SAM2 : SEEK filter
•SAM3 :3D VAR
SATELLITE
observations
IN SITU
observations
DATA
SSALTONEMO usersCORIOLIS
meeting 2006
Forcing Fluxes
& RTG_SST
The Mercator-Ocean forecasting systems
satellite altimetry
+ RTG_SST
+ in situ data
satellite altimetry
PSY2G v1
PSY1 v2
Reanalysis 1992-2002
Impact studies
Oceanic initial conditions
for seasonal forecasts
satellite altimetry
+ RTG_SST
+ in situ data
satellite altimetry
PSY2 v2
PSY3 v1
North Atlantic prototypes:
medium (1/3°) and high resolution (1/15°)
Based on:
1. OPA 8.1 model, 43 vertical levels
Two configurations: North Atlantic 1/3° horizontal resolution
North Atlantic + Mediterranean 5 to 7 km hor. resolution
2. PALM_research software (CERFACS)
modularity of the coupling model-data assimilation system
3. SAM1v2 data assimilation system:
•
•
•
Reduced-Order Optimal Interpolation (ROOI) technique based on SOFA (LEGOS)
1D vertical multivariate Empirical Orthogonal Functions (EOFs)
multivariate assimilation of SLA from JASON-1, ENVISAT and GFO, RTG_ SST,
REYNAUD SSS climatology and T/S vertical profiles provided by the CORIOLIS
centre.
In development: ATL4 & ATL12 (OPA-NEMO), 50 vertical levels with the SEEK
filter  assimilation of SLA, SST HR and T/S profiles using up to 200 multivariate
3D modes for background errors
OSE : Impact of PIRATA data
PSY1v2 Time serie of temperature profiles
In-situ measurements
at
SAMBA mooring (EQ-35°W)
With assimilation of PIRATA data
Without assimilation of PIRATA data
Mercator PSY1v2 Reanalysis: MERA 11 1992-2002
Climate : temperature anomalies
PSY1v2
350m
NAO + 1994
Cold Subpol Gyre
Warm Gulf Stream
NAO - 1998
Warm Subpol Gyre
Warm Subtrop Gyre
PSY2v2, the Mercator High Resolution Forecasting System
for North Atlantic and Mediterranean Sea
An example: Eddies in the Gulf of Mexico
PSY2v2
Origin, separation and westward progression
of an anticyclonic eddy
(mid-June to mid-October 2004)
• Very good spatial and temporal agreement between model
SSH and satellite Chlorophyll concentration (not assimilated)
• Warm eddies are characterized by a weak
chlorophyll concentration
6 weeks from 25 July 2004 to 4 September 2004
Chlorophyll-A (MODIS-CATSAT)
SSH (PSY2v2)
PSY2V2 : T/S profiles impact
The Mediterranean Water Outflow
PSY2v2
Climatology
Salinity at 1000m (2004 temporal mean)
Salinity (11°W,40°N) on 15/08/2004
Model
forecast
observation
PSY2v2
North Atlantic prototypes in development:
ATL4 with SAM2-v1
Based on:
1. OPA-NEMO model, ice model, free surface and bulk formulae, 50
vertical levels
2. PALM_MP software (MPI-2)
enhanced modularity of the coupling model-data assimilation system
3. SAM2v1 data assimilation system:
•
•
•
Based on SEEK filter (LEGI)
3D multivariate seasonal anomalies (O2), adaptative variance (P/2), control vecto
(Hbar,T, S, U,V)
Data assimilation of SLA, RTG_ SST, SST HR and T/S vertical profiles.
First analysis increments of salinity and temperature in january 2004
GLOBAL PROTOTYPES
Low resolution
1.
Model: ORCA2 OPA 8.2
free surface, 31 vertical z-levels,
2° hor. resolution and
½° in the tropics
2.
Palm software
3.
Assimilation methods:
–
Operational : Assimilation of
SLA data (OI, Cooper and
Haines lifting/lowering method)
used for seasonal forecasting
&
Eddy permitting resolution
1.
Model: ORCA025 OPA8.2
surface, 46 vertical z-levels,
¼° hor. resolution
free
2.
Palm software
3.
Assimilation methods:
•
Operational: Assimilation of SLA data (OI,
Cooper and Haines lifting/lowering method)
operational since october 2005
Data Assimilation schemes in development:
Multivariate assimilation of SLA and T and S in situ data with 3D modes
(method based on SEEK filter, LEGI)
Multivariate assimilation of T/S in
situ data and SLA with a 3D-var
method
(based
on
ORCAVAR,
CERFACS)
Model in development:
•ORCA025-LIM (50 vertical zlevels, 1m-450m)
•ORCA12-LIM
Validation with independent in situ data
TAO/TRITON moorings in the Tropical Pacific Ocean
PSY3v1
110°W 5°S
140°W O°N
Temperature of the global system
Temperature of the global system
Temperature observed by the TAO buoy
Temperature observed by the TAO buoy
°C
http://www.pmel.noaa.gov/tao/jsdisplay/
A basis for global climate monitoring
Global system heat content in 2005 (0-700m), in 1011 J/m2
PSY3v1
Climate change indicators
Average depth of the 26°C
isotherm in the global
forecasting system
in September 2005
hurricane indicators
Seasonal forecasting activity with ORCA2:
First results obtained with SAM2 (SEEK)
•ALL1: assimilation of SLA, in situ T,S profiles and SST data
(T/P, JASON, ERS2, ENVISAT, ENSEMBLE, RTG_SST)
 Reduced order Kalman filter (SEEK formulation),
with 200 multivariate 3D modes
ALL1 vs Control run
ALL1
Control run
Std dev.
Improvement
(0< means better)
Equipe R&D assimilation
SAM3
Based on ORCAVAR – v1.x
Intercomparion experiment with SAM2
= - 3DVar : OPAVAR version with the « default options » (background
error covariance matrix,…),
- ENACT like experiments: corrected ERA40 fluxes, a=-200W/m2/K, …
- ORCA2: free surface constant volume: daily correction of E-P.
≠ - along track T/P sla assimilated (filtered for ORCA2), MDT Rio V5.1
- observation error covariance matrix: 3D for T and S, 2D for altimetry
computed using the Fu. et al. method (1993): <rr>=<yy>-<ym>
Representativity
SLA, zonal
NEMOerror
users: meeting
2006T mean
Mean HC(2001) – Mean HC(1993) in °C
SSH and heat content
evolution from 0 to 300 m
(1993-2001)
Mean SSH (2001) – Mean SSH (1993) in m
Data: Merged satellite
Products
Assim. in situ + T/P (IAO)
Control
Data
65°N-65°S
Temperature
anomalies (0–
NEMO users
300m/60°N-60°S)
SLA
meeting 2006
global
60°N-60°S
Summary
2006
OPAx and SAMx
OPA8.1
OPA8.2
SAM1v1
SAM2v1
SAM1v2
OPA9
SAM3
•Analysis and 2 week forecasts every week:PSY1V2,PSY2V2,PSY2GV1 and PSY3V1
•Reanalysis: MERA11
•OSE/OSSE:Pirata impact, SSS assimilation from SMOS and Aquarius (Newsletter #21:April 2006)
•Seasonal forecasting
•Reanalysis with ORCA025 planned in 2007 with SAM2.
Perspectives
2006
Upgrade of data assimilation schemes:
SAM2-vx
 A better way to assimilate largest scales (H)
Smoother/IAU
Adaptative covariances (time dependent)
Data assimilation of surface currents (drifters/Radar) and ice concentration
SST HR
Estimation of representativity errors (obs. errors)
Numerical Optimization for huge configuration (ORCA12 400 Gb): PALM_MP using.
SAM3-vx
improvement of salinity assimilation
Improvement of B matrix
Coupling SAM2 with OPA-NEMO configurations:
ATL4 and ORCA025-LIM : end of 2006/ beginning of 2007
ATL12 in 2007
ORCA12 in 2008

The Mercator experience

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