1. HYCOM data assimilation Short term: ▪ Improve current OI based technique Assimilate satellite data (tracks) directly Improve vertical projection technique using synthetic temperature and salinity profiles from MODAS Long term: ▪ Reduced Order Information Filter (ROIF, Chin and Mariano, University of Miami) ▪ The Singular Evolutive Extended Kalman filter (SEEK, Pham et al., P. Brasseur, LEGI) ▪ Reduced Order Adaptive Filter (ROAF) - adjoint under development (R. Baraille) Reference: 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. A NEAR REAL-TIME 1/12 ˚ ATLANTIC HYCOM NOWCAST/FORECAST SYSTEM 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 R. BARAILLE LEGOS/BRESM, Toulouse, France Near real-Time and archived results (updated weekly): http://hycom.rsmas.miami.edu 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. Forecast wind and thermal forcing Revert toward climatological wind and thermal forcing after 5 days Friday 10 days Analysis wind and thermal forcing Assimilation of MODAS SSH anomaly analysis 13 day forecast The model is run once a week, on Friday. The run consists of a 10 day hindcast and a 13 day forecast. Near real-time run cycle 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) The 1/12° Atlantic HYCOM domain SSH on 21 March 2003 HYCOM long term goals for operational prediction ▪.08° fully global ocean prediction system transitioned to NAVOCEANO in 2006 ~7 km mid-latitude resolution Include shallow water, minimum depth 10-20m Bi-polar (PanAm) grid for the Arctic Embedded ice model ▪ Increase to.04° resolution globally and transition to NAVOCEANO by the end of the decade ~3.5 km mid-latitude resolution Good resolution for coastal model boundary conditions globally “Baseline” resolution for shelf regions globally Comparison of SSH to an independent frontal analysis of MCSST observations White/black line is the frontal analysis of MCSST observations performed at NAVOCEANO. Black line represents data more than four days old. 200 400 600 800 200 400 600 800 200 400 600 800 200 400 600 800 Vertical temperature and salinity sections in the Gulf of Mexico 14 March 2003 SSH forecast for 31 March 2003 (initialized on 18 March 2003) November/December 2002 August 1999 - June 2000 Transport sections Mean Standard deviation Velocity section in the Yucatan Channel 500 1000 1500 500 1000 1500 From: Abascal, A. J. et al. 2001 AGU Fall Meeting 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. 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. Observations