Analyzing a Rainstorm Process in Northern Shaanxi in July 2022 Based on FY-4A Satellite Products

Gao Xingxing; Du Lili; Ma Xiaohua

doi:10.16765/j.cnki.1673-7148.2025.02.011

Abstract：To provide a scientific reference for the application of FY-4A cloud images and quantita-tive products in rainstorm weather monitoring and forecasting,using FY-4A cloud images and quantita-tive products,surface observations,MICAPS,NCEP reanalysis and Doppler radar data,this paper ana-lyzes the heaviest rainstorm in Northern Shaanxi in July 11-12,2022 after into the flood season.The re-sults show that the precipitation is mainly concentrated in the daytime of July 11.From 08:00 to 20:00 on the 11th,there were 97 stations with accumulated rainfall exceeding 50 mm(47%),11 stations with rainfall exceeding 100 mm,and 60 stations with hourly rainfall intensity exceeding 20 mm.The FY-4A precipitation estimates also show that the precipitation process was characterized by large rainfall amount,strong extremes and intense hourly rainfall,so it was a severe grade of rainstorm.The high trough and the warm shear of the low vortex were the main influence systems for this severe precipitation process.The existence and maintenance of the upper-air westerly jet belt caused strong FY-4A atmospheric motion vector divergence above 400 hPa in the rainstorm area,superposing the strong convergence area on the left front side of the low-level jet at 700 hPa and enhancing the precipitation intensity.Severe precipitati-on occurred in the developing process of β and γ scale convective cloud clusters in the vortex cloud sys-tem.The surface convergence line was one of the possible triggering mechanisms of β and γ scale con-vective cloud clusters in the vortex cloud system.The FY-4A cloud parameters further reveal the exist-ence of strong convective upward motion in the rainstorm area.FY-4A convective initiation product con-firms that convective cells were embedded in stratiform cloud precipitation echo,and this severe rainfall was directly related to the"train effect"caused by the continuous generation and eastward movement of convective cells.Before the occurrence of the rainstorm,there was water vapor transported from the South China Sea.At 16:00 on July 10,the maximum total amount of FY-4A atmospheric water vapor reached 7 g/kg.On the 11th,the water vapor transport kept strengthening,and the maximum value of the water vapor flux center at the precipitation peak increased to 8000 g·(cm·s·hPa)-1.During this heavy rainstorm process,the area with the maximum depth of the FY-4A tropopause folding corresponded well with the large-value center of potential vorticity.The downward propagation of upper-air large-value wet potential vortices led the upper-air dry and cold airflow invaded the lower layer,making the dynamic tropopause folding.This is the main cause for the occurrence of severe convective weather.