Performance of SMAP and SMOS Salinity Products under Tropical Cyclones in the Bay of Bengal

To compare the accuracy of satellite salinity data of level-3 Soil Moisture Active Passive V4.0 (S-SMAP) and debiased v5 CATDS level-3 Soil Moisture and Ocean Salinity (S-SMOS) before and after tropical cyclones (TCs) in the Bay of Bengal (BoB), this study used the sea surface salinity of Argo (S-Argo) to assess S-SMAP and S-SMOS before and after the passage of 10 TCs from 2015 to 2019. The results indicate that the S-SMAP and S-SMOS agreed well with S-Argo before and after 10 TCs. It can be seen that the correlation between S-SMAP and S-Argo (before TCs: S-SMAP = 0.95S(Argo) + 1.52, R-2 = 0.83; after TCs: S-SMAP = 0.87S(Argo) + 4.34, R-2 = 0.79) was obviously higher than that of S-SMOS and S-Argo (before TCs: S-SMOS = 0.68S(Argo) + 10.38, R-2 = 0.62; after TCs: S-SMOS = 0.88S(Argo) + 3.98, R-2 = 0.58). The root mean square error (RMSE) was also significantly higher between S-SMOS and S-Argo (before TCs: 0.84 psu; after TCs: 0.78 psu) than between S-SMAP and S-Argo (before TCs: 0.58 psu; after TCs: 0.47 psu). In addition, this study compared S-SMAP and S-SMOS during two TCs that swept in nearshore and offshore waters, and the results show good agreement between S-SMAP and S-Argo in the nearshore and offshore waters of BoB. In the BoB, both S-SMAP and S-SMOS can retrieve sea surface salinity well, and S-SMAP is overall better than S-SMOS, but the SMOS salinity product can fill the gap of SMAP from 2010 to 2015.