The Impact of Velocity Data Assimilation from Drifters using the Navy Coupled Ocean 3D Variational Data Assimilation System (NCODA-VAR)

The Navy Coupled Ocean 3D variational Data Assimilation (NCODA-VAR) system is one of the primary tools that the Navy uses operationally to ingest, process, quality and control, and assimilate ocean observations in near-real time in order to regularly update and improve the forecast skill of several different operational ocean prediction systems. One of the deficiencies of NCODA, however, is its ability to accurately resolve submesoscale features. This is primarily because the two predominant sources of data for NCODA are SST and SSH. The spatial resolution of SSH data is typically too coarse to resolve submesoscale eddies, and SST data lacks the vertical correlation with the subsurface to steer the analysis towards any submesoscale feature.

The capability to assimilate velocity observations is currently being added to NCODA, which primarily includes adding additional error covariances between velocity (geopotential), temperature, and salinity throughout the water column. It is believed that the inclusion of velocity data assimilation will improve NCODA's ability to resolve submesoscale eddies. To test this hypothesis, velocity data will be inferred and assimilated from 100s of surface drifters that were recently released (July 2012) in the Northeastern Gulf of Mexico as part of the GoMRI CARTHE drifter experiment. The resulting analyses will be compared to a subset of withheld drifter data to determine any improvement.