Spatial And Temporal Characteristics Of The Short-duartaion Heavy Rainfall And Heavy Rainfall Days Over Southern China

Quality of the CMORPH-AWS merged precipitation product is assessed by comparingto the quality-controlled hourly precipitation records from1190observation stations oversouthern China during the warm season (April to October) of2008-2013. Biases of themerged precipitation product are quantified for six grades of precipitation intensity in6sub-regions, and used to correct the merged precipitation product for each of the region. Thecorrected precipitation product is analyzed to investigate the temporal and spatialcharacteristics of heavy rainfall days (≥50mm day-1) with and without, respectively,occurrences of short-duration heavy rainfall (≥15mm hr-1). The main results are as follows:1)Compared to the rain gauge records, the merged precipitation dataset can better reflect thedetailed spatial characteristics of short-duration heavy rainfall occurrence under distinctiveterrain conditions; however, it underestimates the rainfall intensity and should be correctedaccording to the precipitation intensity over each region to reduce the biases properly.2) Theshort-duration heavy rains contribute about16%to the total rainfall amount regardless oftheir small contribution (1%) to the total rainfall occurrence. The short-duration heavyrainfall occurs most frequently over the coastal regions of South China and Hainan Island,whereas several secondary centers are located over the central Jiangnan Region, the coastalregions of eastern Zhejiang Province, Sichuan Basin, and southern Guizhou Province. Theshort-duration heavy rains occur much more frequently during April-October than in theother months of a year. In a decreasing order, the occurrence frequencies averaged in June–August, April-May, and September-October shift toward smaller values.3) Proportion ofrainy days (≥0.1mm day-1) with occurrence of the short-duration heavy rainfall is <5‰.However, more than68%of the heavy rainfall days have short-duration heavy rainfalloccurrences. Moreover, more than60%of the short-duration heavy rains occur in the heavyrainfall days. The temporal and spatial characteristics of the heavy rainfall days withshort-duration heavy rainfall are quite similar to those of the short-duration heavy rainfall occurrences, while characteristics of the heavy rainfall days without short-duration heavyrainfall occurrences appear quite different. They are most active over central Jiangnan Regionand regions around the middle-and-lower reaches of Yangtze River during April-August, andare most active over regions around Daba Mountains and southwestern Guangxi Provinceduring September-October.4)Similar to the short-duration heavy rainfall, the spatialdistribution of contribution and intensity of heavy rainfall day is different with its frequency.The contribution of short-duration heavy rainfall around coastal regions of South China andHainan Island is greater depends more upon the high frequency rather than average intensity.However, the contribution of short-duration heavy rainfall over Huai River Basin is greaterdepends more upon the intensity rather than frequency.