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A NEAR REAL-TIME 1/12˚ ATLANTIC HYCOM NOWCAST/FORECAST SYSTEM Near real-Time and archived results (updated weekly): http://hycom.rsmas.miami.edu O. M. SMEDSTAD Planning Systems, Inc., Stennis Space Center, MS 39529, USA H. E. HURLBURT, A. J. WALLCRAFT, and P. HOGAN Naval Research Laboratory, Stennis Space Center, MS 39529, USA E. CHASSIGNET University of Miami/RSMAS, FL 33149, USA Abstract A 1/12° HYbrid Coordinate Ocean Model (HYCOM) of the Atlantic Ocean north of 28°S is used in a near real-time nowcast/forecast system. The Modular Ocean Data Assimilation System (MODAS) sea surface height analysis of available satellite altimeter data is assimilated into the model. The surface information is projected in the vertical using the Cooper and Haines (1996, JGR) technique. The model is currently run once a week to produce the nowcasts. The run also includes a 13 day forecast. A web page has been developed showing the near real-time results from the model. The results are compared to independent observations of SST, temperature profiles and frontal locations determined from independent MCSST observations. The frontal analysis is performed at the Naval Oceanographic Office (NAVOCEANO). This system is the first step toward a global 1/12° nowcast/forecast system based on HYCOM that is planned for transition to the Naval Oceanographic Office in 2006. More advanced assimilation techniques will be included in the system as soon as they show increased model nowcast/forecast skill and the system can run within the operational time limits. R. BARAILLE LEGOS/BRESM, Toulouse, France The 1/12° Atlantic HYCOM domain SSH on 21 March 2003 • Horizontal grid: 1/12° (1678 x 1609 grid points, 6.5 km spacing on average) • 28°S to 70°N (including the Mediterranean Sea) • 26 vertical coordinate (σ-theta reference) • Bathymetry: Quality controlled ETOPO 2.5 • Surface forcing FNMOC [wind stress, wind speed, heat flux (using bulk formula), E-P + relaxation to climatological SSS] • River runoff • Buffer zones: 3° north and south with relaxation to monthly climatological T and S (MODAS) Near real-time run cycle The model is run once a week, on Friday. The run consists of a 10 day hindcast and a 13 day forecast. SSH forecast for 31 March 2003 (initialized on 18 March 2003) 13 day forecast Comparison of SSH to an independent frontal analysis of MCSST observations Friday 10 days Forecast wind and Analysis wind and thermal forcing thermal forcing Assimilation of MODAS Revert toward SSH anomaly analysis climatological wind and thermal forcing after 5 days Velocity section in the Yucatan Channel Mean November/December 2002 August 1999 - June 2000 500 1000 1500 Standard deviation 500 1000 1500 Observations Mean normal flow in Yucatan Channel. The blue (gray) shading represents northward (southward) flow. The Yucatan Current flows to the North above 800 m with the maximum near the Yucatan coast. Southward flow into the Caribbean Sea is observed near the surface off Cuba (Cuban Countercurrent). Deep outflows occur in both western (Yucatan Undercurrent) and eastern sides of the Channel, although variability is larger than the mean. White/black line is the frontal analysis of MCSST observations performed at NAVOCEANO. Black line represents data more than four days old. Standard deviation of normal velocity. Largest variability occurs above 300 m, with two maxima, one on the Yucatan Slope and another on the Cuban Slope. Variability is larger than the mean flow except for the Yucatan Current. Vertical temperature and salinity sections in the Gulf of Mexico From: Abascal, A. J. et al. 2001 AGU Fall Meeting 14 March 2003 Transport sections HYCOM data assimilation 200 200 400 400 600 600 800 800 200 200 400 400 600 600 800 800 HYCOM long term goals for operational prediction Short term: ▪ .08° fully global ocean prediction system transitioned to ▪ Improve current OI based technique NAVOCEANO in 2006 • Assimilate satellite data (tracks) directly • ~7 km mid-latitude resolution • Improve vertical projection technique using synthetic temperature and • Include shallow water, minimum depth 10-20m salinity profiles from MODAS Long term: • Bi-polar (PanAm) grid for the Arctic ▪ Reduced Order Information Filter (ROIF, Chin and Mariano, • Embedded ice model University of Miami) ▪ Increase to .04° resolution globally and transition to ▪ The Singular Evolutive Extended Kalman filter (SEEK, Pham et al., NAVOCEANO by the end of the decade P. Brasseur, LEGI) • ~3.5 km mid-latitude resolution ▪ Reduced Order Adaptive Filter (ROAF) - adjoint under development (R. Baraille) • Good resolution for coastal model boundary conditions globally Reference: • “Baseline” resolution for shelf regions globally Pham, D.T., J. Verron and M.C. Roubaud, 1998: A singular extended filter for data assimilation in oceanography. Journal of Marine Systems, 16, 323-340.