Evaluation Of The Accuracy Of GPM IMERG In Various Types Of Precipitation Processes

The precipitation estimation ability of the integrated multi-satellite retrievals for global precipitation measurement(IMERG)was refined evaluated in the study,using the measurements from the dense ground-based gauges for six typhoon precipitations in Guangdong Province from 2015 to 2016,in multiple temporal scales including 1-,3-,6-,12-and 24-hour precipitation accumulation time for different rainfall intensity,such as the light rain,the moderate rain,the heavy rain and the rainstorm,respectively.The ground-based gauges measurements provided by the National Meteorological Information Center of the China Meteorological Administration.Then,the effect of altitude on the precipitation estimation ability of IMERG precipitation estimation was analyzed during the study.In addition,the quantitative precipitation estimation of C-band Dual-Polarization Radar from Nanjing University of Information Science & Technology(NUIST-CDP),calibrated with the groundbased gauges,was used to evaluate the precipitation estimation ability of the IMERG,during the Meiyu,Typhoon,and Squall Line precipitation.The main conclusions are as follows:(1)The duration of precipitation accumulation affects the estimation accuracy of IMERG during the six typhoon precipitations.The consistency between IMERG and the ground-based gauges increases as the increase of precipitation accumulation time,and the random error of relative bias decrease.(2)The accuracy of IMERG with different rain intensity has a large deviation from the ground-based gauges in 1-hour precipitation accumulation.(3)The IMERG overestimate the precipitation and underestimate the probability of light rain.The accuracy of IMERG for light rain needs to be improved.(4)In Guangdong,the relationship between IMERG precipitation accuracy and altitude is not obvious.(5)During the three typical precipitations of Meiyu,Typhoon,and Squall Line in Jiangsu and Anhui province,the quantitative precipitation estimation of NUIST-CDP radar,calibrated with the ground-based gauges,and the IMERG have a good linear correlation.IMERG overestimates the cumulative precipitation estimated by NUIST-CDP during the Meiyu precipitation.During the typhoon precipitation,when the cumulative precipitation estimated by NUIST-CDP is large,IMERG greatly underestimates the precipitation of NUIST-CDP.IMERG performed poorly during the squall line precipitation,because it hardly observed the heavy precipitation.