The Influences of Environmental Factors on the Microwave Scattering Coefficient from the Sea Surface

The relationship between the microwave scattering coefficient from the sea surface and wind field has been extensively studied. Nevertheless, recent research on air–sea coupling has shown that sea–air temperature difference (SATD) also significantly affects the scattering coefficient. Therefore, to reveal the influence of different environmental parameters, such as salinity, sea surface temperature (SST), and SATD on the scattering coefficient, a theoretical analysis has been carried out firstly. Meanwhile, the coupling coefficient between a scattering coefficient anomaly (SCA) and sea–air temperature difference anomaly (SATDA) over four typical sea regions is compared with that between an SCA and sea surface temperature anomaly (SSTA) by using the nearly 7–year data of the ECMWF, AMSR-E, and QSCAT. The results demonstrate that SCA is more sensitive to SATDA than SSTA. The values of ksatda between the SATDA and SCA exhibit seasonal variation, being higher in summer and lower in winter. Specifically, ksatda can reach a maximum of 0.62 in summer and drops to 0.2 in winter. Furthermore, the effects of the regional monthly mean sea surface temperature (RMMSST), regional monthly mean air temperature (RMMAT), regional monthly mean sea–air temperature difference (RMMSATD), and regional monthly mean wind speed (RMMWS) on ksatda are also discussed in detail. It is found that the RMMSATD is a crucial factor influencing ksatda. And the negative correlation coefficient between the RMMSATD and ksatda is −0.81.