风云卫星微波大气探测资料精度评估与云检测技术研究

Satellite observation is an important data source to improve the initial field of numerical weather prediction and the accuracy of prediction. China's newly launched FengYun 3D (FY-3D) satellite was officially put into operational use on January 1, 2019. Its microwave temperature sounder (MWTS) and microwave humidity sounder (MWHS) could detect global atmospheric vertical temperature and humidity information. In addition, cloud detection is an important part of quality control when assimilating these satellite data. However, FY-3D microwave sounders lack two low-frequency window channels for cloud liquid water retrieval, thus new cloud detection techniques need to be studied. This project intends to use high-precision occultation data at home and abroad, to evaluate and revise the accuracy of FY-3D satellite microwave data based on CRTM and ARMS, the first generation of fast radiative transfer model system in China, and to develop cloud detection technology for FY-3D satellite microwave sounding data. The cloud detection technologies include algorithms based on the existing window channel of a single microwave detector and paired oxygen MWTS and MWHS sounding channel with the same peak weighting function altitude. At the same time, the satellite data assimilation experiments on typhoon cases will be carried out using the GRAPES three-dimensional variational assimilation system. The results of this research will promote the application of FengYun satellite data in assimilation of numerical weather prediction model and will finally improve the accuracy of numerical weather prediction.

卫星观测是改进数值天气预报初始场、提高预报精度的一种重要数据源。我国新发射的FY-3D卫星搭载的微波温度计和微波湿度计可探测全球大气垂直温度和湿度信息。将这些资料同化应用到数值预报模式之前，需要对资料精度进行全面评估和验证；此外，云检测是同化卫星资料时质量控制的重要环节，然而FY-3D微波探测仪缺乏用于反演云液态水的两个低频窗区通道，因此需要研究新的云检测技术。本项目拟采用高精度的国内外掩星探测资料，基于快速辐射传输模式CRTM和中国第一代快速辐射传输模式ARMS，对FY-3D微波探测资料进行精度评估和资料订正；并开展针对FY-3D微波探测资料的云检测研究，包括基于单个微波探测仪现有窗区通道的云检测、以及两个探测仪双氧探测通道配对的云检测；同时依托GRAPES三维变分同化系统，选择台风个例开展卫星资料同化试验。项目研究成果将促进风云卫星资料在数值预报同化中的应用，提升数值模式的预报水平。

只有清楚正确地认识卫星资料观测误差，才能真正用好卫星资料和发挥效能。在本项目（编号：41905036）的支持下，围绕风云卫星微波探测资料评估和云检测技术开展相关研究工作。基于快速辐射传输模式CRTM、RTTOV和中国第一代快速辐射传输模式ARMS，采用高精度的国内外掩星探测资料，对FY-3D微波探测资料进行了精度评估。此外，云检测是同化卫星资料时质量控制的重要环节，FY-3D MWTS和MWHS缺乏用于反演云液态水的低频窗区通道，无法用传统方法进行云检测。在本项目的支持下，研发了基于FY-3D MWTS和MWHS现有窗区通道的新的云检测技术，包括基于单个微波探测仪现有窗区通道的云检测、以及两个探测仪双氧探测通道配对的云检测技术，解决了在缺少23.8和31.4 GHz两个低频窗区通道的情况下，如何利用仪器现有通道对FY-3D 微波温/湿度计资料进行云检测的技术难题。同时依托中国气象局全球四维变分同化系统CMA-GFS，对微波探空资料进行了为期一个月的同化试验。本项目的开展对于改善数值预报初始场、完善微波探测资料同化的质量控制方案、提升数值模式的预报水平具有重要意义。