An OGCM assessment of blended OSCAT winds

Abstract

Ensemble optimal interpolation technique has been used to blend winds for the years 2011-2012, derived by OSCAT, a scatterometer onboard the satellite Oceansat-2, with winds from two different numerical weather prediction (NWP) centers, namely, National Center for Environmental Prediction (NCEP) and European Centre for Medium Range Weather Forecast (ECMWF). These blended winds, when compared with buoy winds, show higher correlations and lower root-mean-square errors (RMSE) than the standalone NWP winds. Analysis of divergence and curl of wind stresses also suggests that the blending is physically realistic. Comparisons of blended winds with buoy winds and analysis of divergence and curls as also the subsequent spectral analysis show that the blended ECMWF wind is the best among all the wind products. Consequent assessment of the impact of blended ECMWF wind product has been done using an ocean general circulation model (OGCM). The technique of empirical orthogonal function (EOF) analysis has been used to assess the impact on sea level and surface currents. The dominant modes of simulated variability in the case of forcing by blended winds are found to be more faithfully reproducing the well-known features of global ocean circulation. Validation of the depth of the 20°C isotherm (D20) also establishes the relative superiority of the blended wind product. ©2013. American Geophysical Union. All Rights Reserved.