Comparative analysis of application effects of three cloud parameters of FY-4A in a rainstorm case

The parameters of cloud macro-and microphysical characteristics (referred to as "cloud parameters") are important basis for cloud and precipitation analysis. Aiming at an extreme rainstorm event that occurred in Hubei province on June 27, 2020, the original data of three band and three cloud parameter products of FY-4A were selected to compare with spatio-temporally coincident MODIS data. The results show that: (1) Compared with the narrow spectrum of MODIS, the spectral response function of the FY-4A satellite generally has a wider band. At the center band of the three channels, there is a certain offset in position between the two. (2) Judging from the original data, the plane distribution modes of the two satellites are relatively consistent. The reflectivity of FY-4A in the visible band is generally lower than that of MODIS, with a correlation coefficient of 0.91 and an average deviation of-0.07. The reflectivity of FY-4A in the near-infrared band is nearly 40% larger than MODIS, with an average deviation of 0.05 and a correlation coefficient of only 0.42. The brightness temperature of the FY-4A infrared band is slightly higher than that of MODIS, with an average deviation of 3.7 K, a correlation coefficient of 0.93, and a linear fitting slope close to 1. (3) From the perspective of cloud parameter products, the Cloud Optical Thickness (COT) of FY-4A retrival is smaller than that of MODIS, and the deep closed cloud area has an obvious difference, but the correlation is good, and the fitting of the two is nonlinear. Compared with MODIS, Cloud Effective Radius (CER) obtained by FY-4A retrival is narrower, Cloud Top Temperature (CTT) is slightly higher, and the correlation is the best. (4) With the increase of rain intensity, the deviation of COT and CER retrieved by the two satellites increases, and the deviation of CTT decreases.