FY-4A干涉式大气垂直探测仪(GIIRS)资料云检测技术

Cloud detection technique research for Geosynchronous Interferometric Infrared Sounder(GIIRS)on FY-4A platform

目前FY-4A/GIIRS资料同化中直接采用多通道扫描成像辐射计(AGRI)的云检测结果,云污染视场内全部通道被剔除,部分可用通道信息丢失。为了获得这些可用通道信息,基于McNally给出的云检测原理,利用GIIRS观测和RTTOV模拟晴空结果,结合GIIRS灵敏度等辐射特性,提出了自主的GIIRS云检测方法。结果表明:GIIRS与AGRI的云检测结果一致性较好,当GIIRS视场中存在细云或碎云时,二者存在一定差异;利用得到的云顶高度,可获得云污染视场中的可用通道,通道使用率增加13.76%。该云检测方法为GIIRS资料同化提供了重要参考。

Currently the FY-4A/GIIRS data assimilation directly uses the cloud detection product from Advanced Geostationary Radiometric Imager(AGRI),and the whole channel data has to be removed when the corresponding IFOV is contaminated by cloud,leading to the loss of some available channel information.In order to improve the utilization rate of those data,a cloud detection algorithm is set up with both GIIRS observation and RTTOV simulation by adopting the method given by McNally,together with radiation characteristics such as GIIRS sensitivity.The results of the proposed method are generally identical to those from the AGRI CLMs,where some minor differences will occur for IFOVs with a certain of fractus.Using the derived the heights of cloud top for each IFOV,the clear channels with respect to the cloud IFOVs can be identified with the data utilization increased by around 13.76%in statistics.This proposed cloud detection algorithm can provide an important reference for GIIRS data assimilation.