Sea surface temperature effects on SAR backscatter

SAR-derived winds and scatterometer wind retrievals are commonly produced utilizing algorithms that assume neutrally stable atmospheric conditions. These conditions are not always met. In particular, significant changes in atmospheric stability across sea surface temperature (SST) fronts are observed. These changes can clearly impact the accuracy of the wind speed products. The effect of SST changes across Middle Atlantic Bight thermal fronts on the observed RADARSAT-1 SAR normalized radar cross-section is examined. Both, lower stability conditions over upwelling regions and unstable conditions over the warmer waters of the Gulf Stream are considered. A simplified frontal model is used to derive a coefficient of thermal stability that relates changes in SST, which serve as proxy for changes in stability, to observed backscatter changes across a frontal region. The effect of these changes on the retrieval of SAR-derived winds and scatterometer wind retrievals is then discussed.