A high-resolution global ocean model of ROMS and its application to GRACE

Frank Colberg and Y. Tony Song
Jet Propulsion Laboratory, CA, USA

We report on a high-resolution global ocean modeling effort using the regional ocean modeling system (ROMS-Rutgers version). This study is motivated by the availability of increasingly accurate measurements of the earth gravitational field (e.g. GRACE), which allow for the deduction of ocean bottom pressure and hence an estimation of the total oceanic mass flux. Since ocean models using Boussinesq approximation a priori inhibit the calculation of ocean bottom pressure signals our effort is directed towards developing a global ocean model with non-Boussinesq formulation.

At the current developing stage we are able to present preliminary results from the initial spin-up phase of the hydrostatic model version. The model resolution is on average ¼ degree horizontally, with highest resolution over the equatorial belt decreasing towards the subtropics to midlatitudes. To overcome the north-pole singularity the grid has been rotated following Madec and Imbard (1996). The ocean model is then coupled to a Sea-Ice model at the poles, hence allowing for a more realistic representation of fresh water fluxes there and for the investigation of possible Ocean-Ice interaction. The model is spun-up with monthly climatologies of the NCEP/ NCAR Reanalysis and then run with monthly means of NCEP/ NCAR windstress and fluxes from 1948 to present.