Typhoon Rainfall Inversion Technology And Error Analysis Based On Fengyun-4 Sensor

Rainfall is an important part of water cycle and energy exchange in the climate system.Extreme weather and climate events(floods and droughts)of rainfall have an important impact on human production and life.Typhoons in the Northwest Pacific carry a large amount of heavy rainfall every year.Rainfall and flood,debris flow and landslide caused by rainfall cause serious losses to coastal cities.Accurate observation and prediction of rainfall is significance for disaster prevention and mitigation.Many satellites in orbit at home and abroad provide accurate data for rainfall forecast and rainfall area monitoring.In this paper,the brightness temperature images of FY4-A's geostationary satellite sensors are used to retrieve rainfall,and the factors affecting rainfall retrieval are analyzed.The main research results are as follows:(1)Research on typhoon rainfall retrieval algorithm based on FY4-A's geostationary satellite brightness temperature images.This paper uses the cloud top brightness temperature images observed by FY4-A multichannel scan imagery radiometer(AGRI)to retrieve rainfall by improving the predictors and parameters of GOES-16 quantity precipitation estimate(QPE).IMERG(the integrated multi satellite retrievals for GPM)rainfall product of global precision mission(GPM)is used for calibration and verification.From 12 to 14 August,2019,the mean root mean square error(RMSE)of rainfall rate(mm/h)retrieval results in the Northwest Pacific region is 3.38 mm/h.Retrieval rainfall data of 11 typhoons in 2019,clearly depict the rainfall region and rainfall distribution of the typhoon,as well as the change and distribution of the typhoon spiral rainfall belt in the process of typhoon enhancement.(2)Research on rainfall cloud's moving speed algorithm.This paper presents a calculation method of the rainfall cloud's moving speed in typhoon area,and then analyzes the influence of the rainfall cloud's moving speed on the error of rainfall retrieval.Through the correlation matching of rainfall gradient in typhoon area,the moving speed of rainfall cloud is deduced by tracking the rainfall cloud.By comparing the rainfall cloud's moving speed with the maximum wind speed of thphoon in Typhoon network of Central Meteorological Station,we know that the rainfall cloud's moving speed increases with the increase of the maximum wind speed of typhoon,and decreases with the decrease of the maximum wind speed of typhoon.(3)The error analysis of rainfall retrieval.By comparing the rainfall rates RMSE corresponding to the rainfall cloud's moving speed of typhoon,the results indicate that the error of rainfall retrieval increases with the increase of the rainfall cloud's moving speed,and decreases with the decrease of the rainfall cloud's moving speed.At the same time,the rainfall retrieval results indicate that the rainfall rate RMSE increase when the maximum wind speed of the typhoon increase.The rainfall rate RMSE in the mature stage of typhoon is about 20%larger than that in other stages,and the rainfall rate RMSE in the decline stage of typhoon is the smallest in the whole typhoon stage.