1/12° Atlantic HYCOM (~8 km resolution in the Gulf of Mexico), 1/8° global NCOM (17 km resolution), 1/24° Intra-Americas Sea (IAS) NCOM (6 km resolution), 1/16° global NLOM (8 km resolution), and 1/32° global NLOM (4 km resolution) are compared to ocean color from SeaWiFS in the Gulf of Mexico (2 June 2003-29 Sept. 2003). All assimilate the operational 1/8° MODAS sea surface temperature analyses of AVHRR data and satellite altimeter sea surface height (SSH). GFO (through 5 Sept.) and JASON-1 altimeter data were used. The NLOM systems assimilate altimeter track data using the model forecast as a first guess. The altimeter data is projected downward using EOF regression (Hurlburt et al., 1990: JGR-O) based on model statistics. The HYCOM and IAS NCOM systems assimilate the operational 1/4° MODAS SSH analyses which are model independent. The 1/8° global NCOM system assimilates the 1/16° global NLOM SSH. HYCOM projects SSH downward using the technique of Cooper and Haines (1996; JGR-O) and the NCOM systems assimilate synthetic temperature and salinity profiles based on SSH, SST and statistics of the historical hydrographic data base. All use atmospheric forcing from the Fleet Numerical Meteorology and Oceanography Center (FNMOC) Navy Operational Global Atmospheric Prediction System (NOGAPS). The SeaWiFS imagery is a composite of the most recent cloud free pixel over the preceding 6 days.

The results are presented in 4 panel images with model SSH contours overlain on SeaWiFS imagery. One system is excluded on each image, the 1/8° NCOM system in the case of the 4 snapshots below. Each of the 3 animations compares 4 of the 5 systems with SeaWiFS. Both bright and dark areas of ocean color are very informative. Both the Loop Current and shed eddies show up clearly as especially dark areas of low chlorophyll. When the model matches well, the dark area is pretty well hidden, but mismatches show up clearly and the 4-way comparison is very effective in bringing this out. The bright areas of high chlorophyll tend to be advected into plumes by strong currents but sometimes also occur in the center of cyclonic (counterclockwise) eddies. The SSH contours are colored prismatically from low (violet) to high (red). Cyclonic eddies are relative lows and anticyclonic are relative highs.

Movies	Gulf of Mexico Model SSH vs SeaWiFS Ocean Color	Period of Comparison
1024x768 fli 1280x1024 fli	(a) 1/16° global NLOM (b) 1/24° IAS NCOM (c) 1/32° global NLOM (d) 1/12° Atlantic HYCOM Sample Snapshots: 9Jul2003 S M L 19Jul2003 S M L 26Jul2003 S M L 8Aug2003 S M L	Jun - Sept 03
1024x768 fli 1280x1024 fli	(a) 1/16° global NLOM (b) 1/8° global NCOM (c) 1/32° global NLOM (d) 1/12° Atlantic HYCOM	Jun - Sept 03
1024x768 fli 1280x1024 fli	(a) 1/16° global NLOM (b) 1/8° global NCOM (c) 1/32° global NLOM (d) 1/24° IAS NCOM	Jun - Sept 03