A Study on SST Dependent Biases in SCATSAT-1 Retrieved Winds

In the present study an evaluation of SCATSAT-1 retrieved winds for the period of October, 2016 to May, 2019 using ECMWF Analysis winds is performed. Comparison results shown on monthly scale clearly demonstrates that the SCATSAT-1 retrieved winds are having excellent and consistent quality with an RMSE of <; 1.5 m/s and <; 16 deg, for wind speed and direction respectively, with near zero overall Bias. These values are observed to be well within the mission specifications of 1.8 m/s and 20 deg for wind speed and direction respectively. However, spatial analysis of monthly wind speed Bias shows systematic and preferential negative biases reaching up to 1 m/s in the southern hemisphere during summer months of October to February. Using collocated SST data from ECMWF Analysis we show here that the underestimation of SCATSAT-1 retrieved winds is observed mainly during low wind speed and low SST conditions due to dampening of the radar backscatter.