Diurnal Variation Characteristics of Precipitation in the Shiyang River Basin of Northwest China in Summer

Abstract

Based on the hourly precipitation data from 32 regional meteorological stations and 5 automatic meteorological stations in summer (from June to August) over the Shiyanghe River basin from 2009 to 2013, we analyzed the diurnal variation characteristics of precipitation over the Shiyanghe River basin, by using four precipitation indices (hourly precipitation, hourly precipitation frequency, hourly precipitation intensity, and different duration precipitation). The results show that the spatial distribution of hourly precipitation, hourly precipitation frequency in summer declines from upstream to downstream over the Shiyanghe River basin because of geographical position, altitude, latitude and weather systems, and the spatial distribution of hourly intensity is complex. The precipitation, the precipitation frequency and the precipitation intensity over the Shiyanghe River basin present a diurnal pattern of double-peak distribution, with the peak periods at 01:00-09:00 and 14:00-23:00, strong precipitation present single-peak with the peak period at 14:00-23:00. Total precipitations and precipitation frequencies of 1 - 3 h short-time rainfall are more than long time rainfall continued more than 10 h over the Shiyanghe River Basin. The short-time rainfall continuing within 1 - 6 h often occurs from afternoon to evening, the long time rainfall continuing more than 6 h often occurs from evening to early morning or late afternoon to evening.