Global Ocean Reanalysis Simulations at Mercator Océan GLORYS1: the Argo years

Transcription

1 Global Ocean Reanalysis Simulations at Mercator Océan GLORYS1: the Argo years Laurent Parent, Nicolas Ferry and the Mercator Océan team Mercator-Océan, Toulouse, France:

2 Outline - Mission of Mercator Océan Current situation of the different ocean forecasting systems Description of the Data Assimilation System - First results of the GLORYS1 simulation: the Argo years Oct Dec Summary and Future plans

3 Mission of Mercator Océan * To develop and operate different ocean forecasting systems, based on OGCM model and advanced data assimilation schemes * MyOcean european project : development and pre-operational validation of a GMES Marine Core Service. Mercator Océan will become a main contributor for the delivery of regular and systematic information to intermediate users & downstream service provider * To accomplish this mission during years, Mercator Océan have to operate : - PSY4: global high resolution (1/12 ) prototype - Reanalysis with global medium resolution (1/4 ), 3 Streams (Argo years, altimetry years, 1958-today) - European Facade (1/36 ) - intermediate systems, already operational, now for R&D and customer contract (French Navy) PSY2 : North Atlantic high resolution (1/12 ) PSY3 : Global medium resolution (1/4 ) will be used for reanalysis

4 Today at Mercator Océan * Status of the Global High Resolution system : Demonstration phase performed during spring 2008, Mersea task done in time. Memory size ~ 700Gb, much bigger than Météo France systems. Now it is in standby, R&D and validation are performed with other systems. Efforts devoted to optimization * PSY2-3 systems : operational since last spring, good performances * Reanalysis : Stream December 1st: 2 years of GLORYS1 done, end of integration in Jan-Feb 2009 based on PSY3V2R2 prototype (global, 1/4 ) + large customization The tuning will be transferred into the new release of PSY3v2R3 (Marie Drévillon) * European Facade system (1/36 ) : Mainly R&D activity on the model component. Data Assimilation and setup of the system in 2009

5 Mercator Océan and Concepts-GOAPP * Mercator started in 1995 French initiative: French Navy, Meteo France, CNES, Ifremer, CNRS * The support of the European Union is of main importance for R&D activities and to be fully operational * Pierre Bahurel is the boss of Mercator Océan and the pilot of My Ocean he s overbooked Eric Dombrowsky and you too collaboration between Concepts-GOAPP and Mercator Océan is drowsing since 2006 Tiger meeting and will be reactivated in the forthcoming months * The SAM-Export version of the Ocean Data Assimilation System is almost ready A political agreement has to be setup * The Ocean-Atmospheric coupling is not in the mandate of Mercator Océan It is included in the mandate of CMC. It might be a good axis of collaboration (own point of view)

6 Overview of the SAM2 Assimilation System * Since 2003, Mercator developed a new assimilation system: SAM2 take a while - Based on Reduced Order Extended Kalman filter - Error covariance matrix is represented by an ensemble of anomalies of a reference simulation (340 multivariate modes, SSH, T, S, U, V) - It is a multivariate and multidata system with a «purely statistical correction» ex: one SST observation could generate a correction of velocity in deep ocean!! - Local analysis, influence bubble for data, see Houtemaker and Mitchel (2001) or Oke et al. (2006) - First Guess at Appropriate Time (FGAT) procedure to calculate innovation vector - Incremental Analysis Update (IAU) approach, to limit the restart procedure - Weekly analysis: wednesday - Dedicated to control mesoscale dynamics in open ocean (not coastal) - Assimilate along-track altimetry data, NCEP RTG SST and insitu data from Coriolis / Ifremer - Use NEMO OGCM: OPA ocean model and LIM2 or LIM2+ sea-ice model - Surface fluxes are estimated by CLIO bulk formulation, no more SST relaxation - GPCP (Global Precipitation Climatology Project) rainfall correction - ECMWF forcing fields (note that NCEP RTG SST is used as lower boundary condition)

7 Overview of the SAM2 Assimilation System * What about performances, sensitivity to observation operator or data error : - Compare to the previous data assimilation system (SAM1), it is more steady, same behaviour at High or Medium Resolution, Global or North Atlantic domain - Can assimilate a large amount of data (there is still a limit!), no super-observation - Better «3D spatial interpolator», less noisy, more consistent with model dynamics Results depend on : - the choice (quality and quantity) of the error covariance matrix - the representativity error (for altimetry, SST or insitu data) - the space / time coverage of the observations - observation operator: ex for SST innovation if smoothed data smoothed first guess - Results are very sensitive to the observation error : We use estimated observation errors, there is no deal with these parameters (0.6K for RTG SST) Now, the NEMO+SAM2 system is mature. Mercator is confident in using it

8 Background error specification from an ensemble of anomalies in the SAM2 scheme Main Idea: Try to generate an ensemble of anomalies with a method close to an ensemble approach Two ways for increasing the number of anomalies: - number of simulations - the length of the simulation SAM2 covariances are represented by an ensemble of anomalies, no truncation + Adaptative scheme for the background error variance : We adjust forecast error at each assimilation cycle in order to be consistent with innovation statistics (internal consistency criterion, see Talagrand 1998)

9 Background error specification from an ensemble of anomalies: Spatial distribution of Pf for a single observation of SST (1 C) Pf on the 1st February What is the impact of a SST increment of 1 C on the SST representer for a grid point serie over the North Atlantic? - Variable sizes of covariances - Strongly anisotropic covariances a classical analytical gaussian shape of pdf s is not well suited It implies to load error modes : good I/O performances on HPC system Grid point serie of SST representers for a SST increment of 1 C. (244 anomalies calculated from a free simulation, NATL4 North Atlantic ¼, NEMO)

10 Reanalysis System: new SST observation operator First guess of model SST NCEP RTG SST First guess of model SST, with smoothing filter NCEP RTG SST is very smoothed compared to the model dynamics apply a smoothing filter on the first guess - impact close to the coast and in area with mesoscale activity - better estimate of the SST innovation vector, less noisy - it allows a better estimate of the T S U V increments

11 GLORYS: Global Ocean ReanalYsis & Simulations Obtain an eddy permitting (1/4 ) realistic 4D description of the ocean history, i.e. : close to the available observations in agreement with the OGCM physics that could be used by various users and for various downstream applications : embedded physical models, global PISCES biological model, can update background error French initiative: Mercator Océan, DRAKKAR community, Meteo France, CLS, + collaboration at european level: MyOcean projet + european ECMWF and CALYPSO (N. Pinardi) proposals are in discussion

12 GLORYS: different Streams Obs. / 7 j. GLORYS-1 Stream1: ARGO GLORYS-2 Stream2: altimetry GLORYS-3 Stream3: ERA-40 Time schedule: 2008: 2009: T/S prof.: 2000~4500 SST: 0,5 x0,5 0,1 x0,1 SLA: ~75000 T/S prof.: ~1000 SST:1 x1 SLA: 12000~50000 T/S prof.: 800< SST: 1 x1 or coarser SLA: NO DATA Stream1 Stream2 Stream3

13 Status of GLORYS1: Argo years We use operational Meteo France computers: NEC-SX8 then SX9 in Simulation is running all the time except Wednesday - 1 node, 8 proc. 72Gb days cycles per day about 3 months for the complete integration - Archive: Meteo France, CNES, local storage 17Gbs per cycle.14.7 for netcdf native grid files (real*4) daily mean output, keep only one restart every 10 cycles 6-7 Tbs of data, monthly means available for diffusion to the Drakkar community - Customisation of the operational chain: - to deal with numerous data base - to limit human intervention - Basic validation is performed in an automatic way - Every 6 months of integration there is a status of the reanalysis (pdf file) - All data transferts and most of the.gif figures are generated in an automatic way But sometimes I need to make an intervention!! It is not perfect...

14 Results of the GLORYS1V1 simulation: Oct 2001 Déc First, Integral quantities: very useful to identify bugs Time evolution of the mean SSH: to be compared with altimetry seasonal cycle Evap-Precip: no drift OK

15 Results of the GLORYS1V1 simulation: Oct 2001 Déc bias ~ 13 W/m2 ERP: sea-surface salinity damping only under sea-ice. Pb with the time interpolation of the Levitus climatology bug fixed in 2003 Total Heat flux: misbalance between CLIO bulk formulation and RTG NCEP SST Bill Large s suggestion: global qt = 0. + addition of a correct seasonal cycle. G. Garric is working on it, available for the next Stream

16 Global Mean and Rms misfit: Altimetry No bias Rms misfit < 8cm Very steady all along the time period: thanks to IAU procedure

17 Global Mean and Rms misfit: SST HR SST products are used in verification mode: - OSTIA SST (UK MetOffice) April 2006 today - ODYSSEA SST (Ifremer/Météo France): data not yet available, OK in 2009 No bias - It is not the priority to assimilate those kind of SST products for reanalysis simulation Rms misfit < 0.5 C

18 Insitu Data: a new insitu database from Coriolis is used (CORA-02) but is not satisfactory (compared to operational or ENSEMBLE/ENACT database) After 4 months of integration GLORYS1V1: February After 4 months of integration PSY3v2R2: February Observation space is different control space too - Behaviour and Performances differents in the southern hemisphere CORIOLIS data center is working on a new reanalysis insitu database

19 Insitu Data: Global scores are not better than PSY3V2R2 It requires much more investigation: insitu data base / heat flux Temp. Data number Mean Misfit Rms Misfit Sal.

20 Temperature increments at 92m depth: After 4 months of integration GLORYS1V1: February 13th 2002 PSY3V2R2: February 14th 2007 Less noisy

21 Salinity increments at 92m depth: After 4 months of integration GLORYS1V1: February 13th 2002 PSY3V2R2: February 14th 2007 Less noisy

22 Currents at 15m depth: GLORYS1V1: December 11th 2003 SURCOUF: similar to OSCAR-NCEP product underestimation in the equatorial band - It requires much more investigation - Validation with TAO array and ARGO drifters - Validation with ADCP data from scientific vessels

23 Currents at 15m depth: SURCOUF: similar to OSCAR-NCEP product underestimation in the equatorial band GLORYS1V1: December 11th 2003 Temp. and Velocity increments injected in the system surface 92m depth

24 Temp. and Velocity increments injected in the system at the surface, December 11 th 2003 European facade Gulf Stream area

25 Vertical velocity: GLORYS1V1: February 13th 2002 much better with IAU approach comparison with the control run has to be done PSY3V2R2: February 14th 2007

26 Vertical velocity: smaller amplitude due to the use of IAU approach GLORYS1V1: February 13th 2002 PSY3V2R2: February 14th especially in the equatorial band - strong impact in the case of the use of a biological model (PISCES)

27 Sea-Ice: first test with LIM2+ in global configuration better results during the summer, LIM2 tends to produce too compacted sea-ice cover FRLD : sea-ice fraction GLORYS1V1-LIM2+ PSY3V2R2-LIM2 Sept Sept CERSAT DATA

28 280 Tide gauges (GLOSS Global Sea Level Observing System): included in the reanalysis system in verification mode (time frequency: 3 hours) No more initial shock after each analysis stage Last month Oct Dec 2003 Churchill St John s

29 Current meters: Dr. G. Holoway (DFO-Sidney) in collaboration with Dr. B. Barnier and Dr. T. Penduff - Greg will validate the GLORYS1V1 simulation with an historical current meters database current meters in 7 approximate areas - the model counterpart of T,S,U,V and SSH will be send to Gregg: 350 Mb per cycle (time frequency: 3 hours)

30 Transports: Florida Bahamas / Gulf of Mexico - Cable data seems to have some Pbs - Good correlation for short time period (a few months)

31 PISCES biological model: Pelagic Iteraction Scheme for Carbon and Ecosystem Studies plug with the reanalysis simulation is underway, courtesy from Dr. A. ElMoussaoui SEAWIFS ORCA025-BIO1 JUN NOV Comparison of the global simulations of Surface Chl using ORCA025-BIO1 (LEFT) with SEAWIFS measurements (RIGHT) for June (TOP) and November (BOTTOM)

32 TCHP: Tropical Cyclone Heat Potential made by the service team of Mercator-Océan (courtesy from Dr. L. Crosnier) July 30th 2008 Depth of the 26 C isotherm TCHP NOAA Mercator PSY3V2R2-ORCA025 US-HYCOM Global 1/12 GODAE intercomparison We intend to estimate the TCHP index with the GLORYS1V1 reanalysis simulation: Oct 2001 Dec 2008

33 Summary and Future plans for Reanalysis: - Thank you to Météo France for computer time & storage facilities - Right now so far, no Pb with the reanalysis chain and the reanalysis system - Large amount of data - Control run has to be performed, in January Validation of such simulation is a long long task. - GLORYS1V2 is supposed to start next summer with: * less bug * new insitu database from CORIOLIS center * improvements on air-sea fluxes, its global balance, seasonal cycle, drift. * new vertical grid (72 levels) * NEMO3, be careful about the plug of a new model * run it on NEC-SX9 * Drakkar meeting will be held in Grenoble on February

34 Summary and Future plans at Mercator Océan: * Since 10 years: From Cooper & Haines (1996) scheme to much more advanced and sophisticated techniques. It takes a while: human efforts, software developments & computer time Strengths of the current system: - Can assimilate a large amount of data (there is still a limit!), no super-observation - Better «3D spatial interpolator», less noisy, more consistent with model dynamics - IAU approach improve results can plug biological model Weaknesses : - Under estimation of the surface currents (15 m) compare to ARGO drifters improve the model - Under correction in deep ocean (> 1500m) no easy solution - CPU & Elapsed time consuming - Not able to control High Frequency signal, as tide * During the MyOcean years: - Most of the tasks are dedicated to optimize, and consolidate the systems - Just a few developments on the system (Ocean / Sea-ice models and Data assimilation): Assimilation of sea-ice data Assimilation of High Resolution SST data products for the European Facade system Assimilation of the SSH signal from tide gaude, warning: observation operator Assimilation of Argo drifters velocity