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Tang, W., Yueh, S., Lagerloef, G., Fore, A., and Hayashi, A. (14-Nov-13)

Rain has an instantaneous impact on sea surface salinity (SSS), but also interferes with microwave remote sensing signals, making the task to retrieve SSS under rainy conditions difficult. A rain correction scheme is developed based on analysis of the L-band radiometer/scatterometer residual signals after accounting for roughness due to wind and flat surface emissivity. The combined active passive (CAP) algorithm is used to retrieve SSS in parallel, with (SSS_{CAP_RC}) or without (SSS_CAP) rain correction. The global monthly RMSE with respect to SSS_ARGO is reduced by about 0.1 PSU. Regional biases between SSS_ARGO, SSS_CAP and SSS_{CAP_RC} are examined in areas with frequent rain events. Results show ΔSSS (i.e. SSS_{CAP_RC}-SSS_CAP) is highly correlated with the seasonal precipitation pattern and reduces surface freshening by about 0.2-0.3 PSU under heavy rain. However, ΔSSS shows no correlation with the difference pattern between SSS_ARGO and either SSS_{CAP_RC} or SSS_CAP. The associated upper layer stratification depicted by ARGO profiles suggests this may reflect the true difference between skin and near surface salinity in high-stratified regions, for example, around the edge of freshwater pools. The effect of ΔSSS on water cycle in terms of mixed-layer salt storage tendency is estimated causing 20% difference in areas with strong freshwater flux.