Spatio-temporal characteristics of short-duration extreme rainfall in the recent ten years in Zhejiang Province

By using hourly precipitation data from the automatic weather stations in Zhejiang Province from 2010 to 2019, the temporal and spatial distribution of SDER (short-duration extreme rainfall, precipitation ≥ 50 mm·h^-1 or 100 mm·(3 h)^-1) are studied. Several results are followed. (1) There are about 169.8 h per year of SDER in Zhejiang Province, mainly distributed in warm season (from May to October) and afternoon (from 14∶00 BT to 21∶00 BT). The eastern coast is a high incidence zone, including two areas: the southeast coast and Hangzhou Bay. (2) SDER appears from May and gradually extends from south to north. The corresponding stations basically cover the whole territory from July to September, and the most influential period is in August with monthly average peak frequency 1.3 h·a^-1 for stations in southeast coast and monthly average peak intensity 99.1 mm·h^-1 for stations in Hangzhou Bay. SDER moves eastward to the sea from October and the process gradually ends. (3) High incidence and intensity of SDER are mostly in the afternoon, with the scope of influence reaching the maximum and the daily variation curve of annual frequency also arriving the peak value 17.4 h·a^-1 at 17:00 BT. During this period, high-frequency stations are concentrated at southeast coast, accounting for 83.2% of the total, while the precipitation intensity in Hangzhou Bay increases significantly, and more than 50% of the stations have exceeded 57.6 mm·h^-1. (4) Topography is highly related to the spatial distribution of SDER. The underlying surface and trumpet-shaped topography of the sea-land interface in the southeast coast contribute to the occurrence of SDER, while the trumpet-shaped landform extending inland in Hangzhou Bay promotes the precipitation efficiency.