Scatterometer and reanalysis wind products over the western tropical Indian Ocean

Accurate knowledge of the wind stress field is fundamental for understanding the ocean dynamics of a particular region. Ocean circulation models typically require this as forcing field and to be specified as one of the boundary conditions. Despite its importance, there are still substantial uncertainties in obtaining sufficiently accurate wind stress fields for many regions as well as sizeable differences between wind stress products for the same region. In this study, an assessment is made of three different wind products (one satellite scatterometer and two reanalyses) for the western tropical Indian Ocean, an area of complex ocean dynamics which has important influences on regional climate. In addition to this assessment, an investigation of the local scale spatial variability in the winds is made. It is found that the wind fields over the western Indian Ocean have prominent semiannual and annual cycles, but there are significant differences in these cycles when comparing different products. For example, for ERA-interim, the annual cycle of wind speed associated with the Somali Jet display a longer Southwest monsoon season compared to QuikSCAT and NCEP. Both the scatterometer and two reanalysis products display analogous large-scale wind features; however, differences were noted in the strengths of wind speed and wind stress curl. It is also evident that the local scale wind features associated with orographic effects are better resolved by QuikSCAT and ERA-interim than NCEP. These differences in wind products have important implications for regional ocean dynamics and modeling.