风云三号A星微波湿度计探测通道定标分析
Calibration Analyses for Sounding Channels of MWHS Onboard FY-3A
中文摘要：
微波湿度计装载在中国新一代极轨气象卫星风云三号卫星上，可完成全天候大气湿度信息的被动微波遥感探测。风云三号A星（FY-3A）微波湿度计（MWHS）在150～191GHz频率范围内有5个通道，为保证在轨定量应用，FY-3A发射之前，在2m真空罐（TVAC）中完成了MWHS真空试验，获得了接收机非线性等基本参数。FY-3A MWHS在轨运行的4年中，性能一直稳定，扫描周期间冷空和热源观测结果的变化一般在20个计数以内；绕地一圈的轨道观测中热源温度变化不超过0.5K。基于从TVAC试验中获得的非线性订正，FY-3A MWHS观测亮温与NOAA-17 AMSU-B及NOAA-18 MHS观测亮温有很好的一致性；FY-3A MWHS与NOAA-17 AMSU-B瞬时匹配点平均亮温差在183±1GHz通道小于1.0K。在观测场与背景场的比较分析中，FY-3A MWHS183.31±1GHz通道的观测和模拟亮温差与NOAA-18MHS具有相同分布特性；而对183.31±7GHz通道而言，FY-3A MWHS与背景场更为吻合。分析表明，FY-3A MWHS数据将有助于数值天气预报。
中文关键词：
FY-3A MWHS，定标，交叉对比
KeyWords：
Calibration, cross comparison, FY-3A MWHS
Abstract：
The Microwave Humidity Sounder (MWHS) is a five-channel microwave radiometer in the range of 150~191 GHz onboard FengYun 3 (FY-3). Before the launch of FY-3A, the intensive thermal vacuum (TVAC) tests for MWHS had been carried out in a 2-m TVAC chamber, and the basic parameters such as receiver nonlinearity were obtained. Four-year operation shows that the performance of FY-3A MWHS remains stabile. The variations among space views and warm target views in the interval of scan lines were generally within 20 counts. In addition, the temperature fluctuation of the warm target in a single pass is within 0.5 K. Primarily, due to the nonlinearity correction obtained from the TVAC test, radiance measurements of MWHS agree well with NOAA-17 AMSU-B and NOAA-18 Microwave Humidity Sounder (MHS) data. Averaged brightness temperature differences between FY-3 MWHS and NOAA-17 AMSU-B, at simultaneous cross-overpass points, are less than 1.08 K for the channels at 183±1 GHz. In the observation-minus-background comparison, the observed and simulated brightness temperature biases of FY-3 MWHS and NOAA-18 MHS exhibit similar performance in the 183.31±1 GHz channel; but in the 183.31±7 GHz channel, MWHS agrees better with background. It is anticipated that FY-3 MWHS data will contribute to numerical weather prediction.