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 M...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.展开更多
数值模式边界层物理过程和初值场条件的欠缺是海雾模拟准确率偏低的主要原因。本文为改进模式初始场,开展针对海雾模拟的卫星观测资料同化试验,将质量控制和偏差订正后的FY-3A卫星微波湿度计(MWHS)和微波温度计(MWTS)的优选通道数据,经3...数值模式边界层物理过程和初值场条件的欠缺是海雾模拟准确率偏低的主要原因。本文为改进模式初始场,开展针对海雾模拟的卫星观测资料同化试验,将质量控制和偏差订正后的FY-3A卫星微波湿度计(MWHS)和微波温度计(MWTS)的优选通道数据,经3DVar(Three-dimensional variational data assimilation)进入WRF模式以试验其对黄、渤海海雾模拟的影响。通过分析静止气象卫星检测到的海雾区模拟大气温、湿场同化分析增量,发现代表环境场条件的海雾类型及模式对其模拟能力的差异,显著影响了同化效果,表现为同化对模式模拟能力较强的平流冷型海雾改进明显,对模拟效果不甚理想的非典型混合过程中的暖型海雾阶段则基本没有改进效果。为寻找原因,对包括海雾区低层大气模拟场逆温结构在内的温湿度场与邻近探空观测进行了对比,分析了随时间演变的海雾格点温、湿场同化分析增量,发现冷型海雾区格点同化分析增量能弥补观测—模拟差异,使气温调减,相对湿度调增,同时水汽和液态水也出现负相关的变化,边界层相关热力动力场同化分析增量在垂直方向也有配合迹象,相比而言,主体是暖型海雾的非典型过程则未见此类现象和其他的有益调整迹象。展开更多
文摘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.
文摘数值模式边界层物理过程和初值场条件的欠缺是海雾模拟准确率偏低的主要原因。本文为改进模式初始场,开展针对海雾模拟的卫星观测资料同化试验,将质量控制和偏差订正后的FY-3A卫星微波湿度计(MWHS)和微波温度计(MWTS)的优选通道数据,经3DVar(Three-dimensional variational data assimilation)进入WRF模式以试验其对黄、渤海海雾模拟的影响。通过分析静止气象卫星检测到的海雾区模拟大气温、湿场同化分析增量,发现代表环境场条件的海雾类型及模式对其模拟能力的差异,显著影响了同化效果,表现为同化对模式模拟能力较强的平流冷型海雾改进明显,对模拟效果不甚理想的非典型混合过程中的暖型海雾阶段则基本没有改进效果。为寻找原因,对包括海雾区低层大气模拟场逆温结构在内的温湿度场与邻近探空观测进行了对比,分析了随时间演变的海雾格点温、湿场同化分析增量,发现冷型海雾区格点同化分析增量能弥补观测—模拟差异,使气温调减,相对湿度调增,同时水汽和液态水也出现负相关的变化,边界层相关热力动力场同化分析增量在垂直方向也有配合迹象,相比而言,主体是暖型海雾的非典型过程则未见此类现象和其他的有益调整迹象。
