Retrieval of sea surface temperature from the scanning microwave radiometer aboard HY-2B

The HY-2B satellite, equipped with the scanning microwave radiometer (SMR), was launched on 25 October 2018 and began observation on 30 October 2018. With the SMR data, we retrieved the sea surface temperature (SST), along with the ocean wind speed (OWS), total columnar water vapour (TCWV), and cloud liquid water (TCLW), within an optimal estimation (OE) Framework. Through the comparison with Argo profiling floats data, mean difference of 0.01 degrees C, and standard deviation of 0.47 degrees C are inferred for SST within the latitude range of 60 degrees S-60 degrees N. The contrast against the WindSat standard products also shows an encouraging result, in which the standard deviation for SST, OWS, TCWV, and TCLW are 0.49 degrees C, 0.64 m s(-1), 1.23 mm, and 0.029 mm, respectively. To investigate the effect of oceanic and atmospheric state on SST retrieval, the sensitivities of brightness temperature (TB) at considered frequency to SST, OWS, TCWV, and TCLW are carefully analysed, and seven combinations of SMR frequencies are tested to retrieve different parameters. The results emphasize the importance of low-frequency observations in retrieving accurate SST and suggest that the influence of wind speed and atmospheric vapour content is non-negligible. It is also indicated that the role of the higher frequency (23.8 and 37 GHz) is limited for SST retrieval. This study presents an assessment for SST retrieval from SMR measured data and provides a reference about frequency selection for measuring SST from passive microwave radiometer.