Cross-calibration between MWRI and AMSR2 to improve consistency of snow depth products

Abstract

The Microwave Radiation Imager (MWRI), boarded on the FY-3 series satellites: FY-3B, FY-3C, and FY-3D, is the first satellite-based microwave radiometer in China, commencing passive microwave brightness temperature data acquisition since 2010. The Advanced Microwave Scanning Radiometer 2 (AMSR2) boarded on the Global Change Observation Mission 1st-Water (GCOM-W1), has been operational since 2012. Despite the FY-3 series satellites are equipped with the same MWRI and all MWRIs sharing comparable parameters and configurations as AMSR2, disparities in observation times and satellite platforms result in inconsistencies in the data obtained by different satellites, which further impacting the consistency of retrieved geophysical parameters. To improve the consistency of brightness temperatures from FY-3B, FY-3C, FY-3D/MWRI, and GCOM-W1/AMSR2, cross-calibrations were conducted among brightness temperatures at ten-channel from above four platforms. The consistency of derived snow depth from MWRIs and AMSR2 in China before and after the calibration were also analyzed. The results show that the correlation coefficients of brightness temperatures at all channels between sensors exceed 0.98. After cross-calibration, the RMSEs and biases of brightness temperatures at all frequencies and snow depth in China derived from them reduce to varying degrees. The consistencies in both brightness temperatures and snow depth of FY-3B/MWRI, FY-3D/MWRI, and AMSR2 are higher than those of FY-3C and others. These findings advocate for the utilization of cross-calibrated brightness temperatures from FY-3B/MWRI, FY-3D/MWRI, and AMSR2, which share similar satellite overpass time, to derived a long-term snow depth dataset.