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MERCATOR OCEAN MODELISATION 1/12° configurations

MERCATOR OCEAN MODELISATION 1/12° configurations. North Atlantic Ocean Global. North Atlantic configurations. Ocean code : NEMO Grid : ORCA Bathymetry : ETOPO + BetMAP + Gebco Initialisation : Levitus Parameterizations : Filtered free surface Partial steps LIM ice model

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MERCATOR OCEAN MODELISATION 1/12° configurations

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  1. MERCATOR OCEAN MODELISATION1/12° configurations • North Atlantic Ocean • Global

  2. North Atlantic configurations. • Ocean code: NEMO • Grid:ORCA • Bathymetry:ETOPO + BetMAP + Gebco • Initialisation: • Levitus • Parameterizations: • Filtered free surface • Partial steps • LIM ice model • Isopycnal laplacian diffusion for the tracers • Biharmonic diffusion on the dynamic • Energy and enstrophy conservating scheme • Monthly climatology for the runoff file (Dai & Trenberth) • CLIO Bulk formula • Atmospheric forcing available: • Daily mean ECMWF operational analyses (period: 1998-2006) • Daily mean ERA40 (1992-2001)

  3. ATL12-T03 simulation • ATL12-T03 configuration: • Domain :1608 x 1551 x 46 • Vertical grid refined at the surface : 46 z-levels (1 to 450m) (DRAKKAR : 46 z-levels (6 to 250 m)) • Atmospheric forcing : • ECMWF operational analyses 2000-2006 : • “Spin up” : twice the year 2000 • CLIO bulk formula • Daily mean forcing flux • No sss relaxation • Outputs : • Fields :3 days mean. • monthly restart files.

  4. General circulation : 2003 Sea Surface Height MSSH 93-99 (M.H. Rio ) SSH 2003 ATL12-T03 -1m 0.86m

  5. Topex/Poseidon EKE 2004 ATL12-T03 EKE 2004 EKE 2004 0 1000

  6. 2.6 3.6 0.8 30.4 32 0.63 25.7 24.4 19.1 5.6

  7. Comparison Gulf stream :ATL12-T03 / Altimetry (aviso) 37N Good location of the Gulf Stream front Cold cells southern of the GS (Same size but more frequent and colder)

  8. Mediterranean EKE in 2003 • Good variability of the Algerian current and Alboran gyre • Strong coastal current in Levantine basin compare to altimetry. Courtesy of PHD I.Pujol 2006

  9. Conclusions • Well reproduced general circulation : GS separation, NAC, North Brazil current,… • Variability comparable to the altimetry data Problems : • Boundaries limits different from NATL4 • Large scale factors between 50-500m induce instabilities : No realistic oscillations

  10. ATL12-T09 : Domain North and south boundaries are now similar to the NATL4 configuration ATL12-T09 NATL4 ATL12-T03

  11. ATL12-T09 : Bathymetry First and last indices of ATL12-T09 domain are issued from the 1/4° bathymetry to prepare OBC with ORCA025 fields.

  12. Decrease ITCZ intensity (tests performed with NATL4) Difference of the SSS : Levitus annual - NATL4 annual (year 3) Réductions en % mm/jours Threshold function applied to the precipitation field between 10°N and 10°S Simulation performed with precipitation not corrected Simulation performed with the threshold function over the precipitation field at the equator. Improvment of the SSS in the tropics. No degradation in the north Atlantic basin. Impact of the correction limited to upper layers (<50m>)

  13. ATL12-T09 : computing • ATL12-T09 configuration: • Domain :1615 x 1585 x 50 • Vertical grid refined at the surface : 50 z-levels • Initial conditions from Levitus climatology • Atmospheric forcing : • ECMWF operational analyses 1998-2006 : • CLIO bulk formula • Daily mean forcing flux • SSS relaxation • Outputs : • Fields :3.3Go/date 3 days mean. • 1 year : 60h elapsed on 224proc (with SMT, 112 “real”) Jpni, jpnj: 24, 13 Jpnij : 224 (-88proc) Total of outputs for the simulation : 2 To

  14. New vertical grid (50 levels) 50 Levels 46 Levels Different vertical grids Temperature (high) and zonal velocity (bottom) at the equator. (date : y2004m07d22) Scales factors

  15. ATL12-T09 : Results y2003 y2001 y2002 Max=18.8 Max=15.5 Max=17.4

  16. ORCA12 : computing • ORCA12 configuration: • Domain :4322 x 3059 x 50 • Vertical grid refined at the surface : 50 z-levels • Memory needed: 510 Go • Atmospheric forcing : • ECMWF operational analyses 1998-2006 : • CLIO bulk formula • Daily mean forcing flux • SSS relaxation ? • Outputs : • Fields :18Go/date (4.5Go in 4bytes) 3 days mean.

  17. Prospects Studies : • Diurnal cycle (3H) NATL4 • Tidal mixing parameterization. • Wave mixing • Test OBC European regional models • lntercomparaison OPA-Symphonie (biscay bay) and extension to OPA-Symphonie-Mars-Hycom Simulations : • Simulation Bulk MEMO_UNITFP with ORCA025_LIM (1998-2006) • First ORCA12 simulation. • Development configuration of the European coast (1/36°)

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