The Rain Effect on Aquarius Sea Surface Salinity Retrieval
[14-Nov-2013] Tang, W., Yueh, S., Lagerloef, G., Fore, A., and Hayashi, A.
Presented at the 2013 Aquarius/SAC-D Science Team Meeting
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 (SSSCAP_RC
) or without (SSSCAP
) rain correction. The global monthly RMSE with respect to SSSARGO
is reduced by about 0.1 PSU. Regional biases between SSSARGO
are examined in areas with frequent rain events. Results show ΔSSS (i.e. SSSCAP_RC
) 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 SSSARGO
and either SSSCAP_RC
. 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.