FPCI and SPCI Are Proposed to Distinguish the Frontal and Saturated Precipitation Systems Based on FY-4A

Infrared (IR) observations from geostationary satellites have been widely used in estimating the precipitation with high spatiotemporal resolutions. Currently, it is acknowledged that single-channel IR observations are capable to extract the properties of cloud tops, while are insufficient for deeper vertical information. However, based on developments of multispectral IR imagers onboard geostationary satellites, distinguishing different precipitation regions with different vertical structures becomes possible, which has not been fully explored yet. Therefore, combining FengYun-4A/advanced geosynchronous radiation imager (FY-4A/AGRI) and global precipitation measurement/dual-frequency precipitation radar (GPM/DPR), we innovatively proposed frontal precipitation cloud index (FPCI) and saturated precipitation cloud index (SPCI) for IR signals by exploiting the characteristic responses of channel combinations to different precipitation systems. It is proven that multispectral IR observations are capable of responding to certain precipitation systems with different vertical structures. Meanwhile, IR imagers onboard geostationary satellites have significant advantages on tracking developing processes of precipitation systems with high spatiotemporal resolutions than microwave detectors onboard low-earth-orbit (LEO) satellites. In addition, this study is beneficial for impelling IR precipitation estimation to consider more radiation-based physical theory, especially for FY-4A official precipitation product.