North Atlantic Ocean OSSE

Nature Run and Forecast Run
The OSSE system for the Atlantic Ocean (98.0ºW to 20.0ºW and 5.0ºN to 45.0ºN) has been setup with two different sets of the HYCOM configurations for the 0.04º Nature Run (NR) and the 0.08º data-assimilative forecast model (FM). For the initial and boundary (through nesting method) conditions, both models use the global HYCOM analysis which has the 0.08º grids in horizontal and the 32 hybrid layers in vertical and is remapped to the 36 vertical hybrid layers for the NR and to the 26 vertical hybrid layers for the FM. Each model uses different bathymetry; the FM uses the same bathymetry as the global HYCOM while the NR uses a new higher-resolution bathymetry which provides more detailed and accurate representation of coastlines. The U.S. Navy NOGAPS atmospheric forcing (winds, surface fluxes, precipitations) is used to force both models with different time frequency, 3hourly for the NR and 6 hourly for the FM. Monthly river discharges for 172 rivers are implemented for both models. Special treatment of area source for the Amazon River has been done for the NR to simulate fresh water spreading better. Also, the sea surface salinity relaxation to the monthly climatology-Generalized Digital Environmental Model (GDEM) has been employed for the NR. Among different configurations between the NR and the FM, vertical re-mappers for layer variables in the vertical grid generator and vertical mixing schemes are significant differences; a WENO-line vertical re-mapper and the KPP vertical mixing scheme for the NR and a piecewise-polynomial (PPM) re-mapper and the GISS level2 algorithm. Both models run from 19 September, 2008 to 8 October, 2013. Evaluations of both modes over the five-year from 9 October, 2008 to 8 October, 2013 are ongoing.
Five-year (2008-2013) mean fields of SSH, current speed at 15m, SST, and SSS from experiments NR and FM are compared to each other and to mean fields of SSH and current speed at 15m obtained from Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) data center, and mean fields of temperature and salinity from the Navy GDEM3 (Generalized Digital Environment Model) ocean climatology. The behavior of the Amazon river plum is also compared among the NR, FM and observations.

Please click on the following links to look at examples of the results of the evaluation of North Atlantic model mean.

SSH and Current speed at 15m
Amazon River plume spreading