Probability distribution of hourly precipitation in typhoons during summer seasons in the southeast China

First, we separated the typhoon precipitation from hourly precipitation data at 818 national meteorological stations by referring the 6-hour CMA-STI tropical cyclone best-track data between 1 July and 30 September from 1980 to 2013. Secondly, we employed the maximum likelihood estimation method to obtain the shape parameter α and scale parameter β of typhoon precipitation probability density in a Gamma distribution, then performed a comparative analysis of hourly precipitation probability distribution observed and simulated by the Gamma distribution at representative stations. Lastly, based on the simulation of the Gamma distribution, we obtained the probability distribution of typhoon precipitation, and the cumulative probability distribution of precipitation exceeding given thresholds and the series thresholds of extreme typhoon precipitation under different influence distance and different intensity of typhoon. The results show that, generally, the areas of the coastal regions of south and east China have the largest probability of 5 mm threshold precipitation. The rest of the regions have a low probability of 5 mm threshold precipitation. The cumulative probability with hourly rainfall over 10 mm threshold is between 10% and 15% in the coastal region of Guangdong, south part of Guangxi and northwest part of Hainan province. The probability with hourly rainfall more than 20 mm threshold is very low in southeast China. With the increase of the intensity of the short distance typhoons, the regions where the hourly rainfall of 15 to 20 mm threshold with 95% cumulative distribution function (CDF) change from Hainan and the coastal region of Fujian and Guangdong to Zhanjiang and Hainan. The regions of hourly precipitation 10 to15 mm threshold with 95% CDF change from Guangdong, Guangxi, Fujian and Zhejiang to Zhejiang and the coastal area of Jiangsu, Guangdong and Fujian provinces. With the increase of the intensity of the long distance typhoons, the areas affected by typhoon precipitation gradually extend from the southeast coast of China to inland, whereas the regions with higher hourly precipitation threshold with 95% CDF are Hainan, Guangdong, Fujian and Jiangxi provinces.