Author: V. Zlotnicki, A.H. Ali and Rui M. Ponte
AGU Fall Meeting, San Francisco
Zlotnicki, V., A.H. Ali, and R.M. Ponte, 2001. Atmospheric forcing of a barotropic ocean model to dealias altimetry and GRACE, AGU Fall Meeting, San Francisco, December 2001.
We use a barotropic model to remove high frequency ocean variability from altimetry and the planned GRACE gravity mission. Wind and pressure forcing are the key external inputs (in addition to bathymetry, and the selection of friction coefficients). The operational agencies (NCEP, ECMWF) change their model configurations frequently, so results obtained even a year ago may no longer apply. Furthermore, these changes themselves introduce near discontinuities in forcing. We compare forcings for 7/2000 through 6/2001 from ECMWF and NCEP (both Reanalysis and operational), and a wind products that incorporates NCEP output and Quikscat data. We also test the effect of considering atmospheric stability in calculating wind stress from model output (NCEP operational output includes wind vector at 10m and 1000 mbar, but not the stress) as well as various stress parameterizations. The barotropic model's output match to both Topex/Poseidon sea level and bottom pressure recorder (BPR) data are the key quality measures. The match to BPR is the more stringent test as far as GRACE is concerned. We also discuss standard approximations used in this model (constant gravity acceleration, constant density), which introduce errors of order 2/1000 in mass variation.