摘要
Microwave Humidity Sounders （MHS） onboard NOAA- 15, - 16, - 17, - 18, - 19, and EUMETSAT MetOp-A/B satellites provide radiance measurements at a single polarization state at any of five observed frequen- cies. The Microwave Humidity Sounder （MWHS） onboard the FengYun-3 （FY-3） satellite has a unique instrument design that provides dual polarization measurements at 150 GHz. In this study, the MWHS polarization signal was investigated using observed and modeled data. It is shown that the quasi-polarization brightness temperatures at 150GHz display a scan angle dependent bias. Under calm ocean conditions, the polarization difference at 150 GHz becomes non-negligible when the scan angle varies from 10° to 45° and reaches a maximum when the scan angle is about 30°. Also, the polarization state is sensitive to surface parameters such as surface wind speed. Under clear-sky conditions, the differences between horizontal and vertical polarization states at 150GHz increase with decreasing surface wind speed. Therefore, the polarization signals from the cross-track scanning microwave measurements at window channels contain useful information about surface parameters. In addition, the availability of dual polarization measurements allows a one-to-one conversion from antenna brightness temperature to sensor brightness temperature ifa cross-polarization spill-over exists.
Microwave Humidity Sounders （MHS） onboard NOAA- 15, - 16, - 17, - 18, - 19, and EUMETSAT MetOp-A/B satellites provide radiance measurements at a single polarization state at any of five observed frequen- cies. The Microwave Humidity Sounder （MWHS） onboard the FengYun-3 （FY-3） satellite has a unique instrument design that provides dual polarization measurements at 150 GHz. In this study, the MWHS polarization signal was investigated using observed and modeled data. It is shown that the quasi-polarization brightness temperatures at 150GHz display a scan angle dependent bias. Under calm ocean conditions, the polarization difference at 150 GHz becomes non-negligible when the scan angle varies from 10° to 45° and reaches a maximum when the scan angle is about 30°. Also, the polarization state is sensitive to surface parameters such as surface wind speed. Under clear-sky conditions, the differences between horizontal and vertical polarization states at 150GHz increase with decreasing surface wind speed. Therefore, the polarization signals from the cross-track scanning microwave measurements at window channels contain useful information about surface parameters. In addition, the availability of dual polarization measurements allows a one-to-one conversion from antenna brightness temperature to sensor brightness temperature ifa cross-polarization spill-over exists.
