Abstract:
Based on the hourly precipitation data of 9 national automatic stations and 136 regional automatic stations in Leshan from 2013 to 2020, the temporal and spatial distribution and variation characteristics of short-time heavy precipitation in Leshan were systematically studied by using statistical diagnostic analysis methods, and the relationship between the frequency of short-time heavy precipitation and topographic factors was discussed. The results show that the average annual frequency and extreme value of short-time heavy precipitation in Leshan showed an increasing trend, the strength was relatively stable. Short-time heavy precipitation occurred from March to October, the monthly distribution of short-time heavy precipitation frequency presented a single peak, which mainly occurred in July and August, accounting for 77.7% of the whole year. The frequency of short-time heavy precipitation from late July to early August accounted for 49.8% of the total from July to August. The diurnal variation of short-time heavy precipitation frequency showed a single peak and single valley structure. The probability of occurrence at night was the largest, and the probability of occurrence in the daytime was relatively small. The high incidence period of short-term heavy rainfall was from 22 : 00 to 04 : 00 next day. Although the probability of short-time heavy precipitation in the afternoon and evening was relatively small, but its intensity was strong. The spatial distribution of short-time heavy precipitation in Leshan was quite different, and there was a characteristic of two-level differentiation, which was closely related to the terrain. Generally, it was less in southwest and northeast, and more in northwest-central-southeast. The occurrence of short-term heavy rainfall was significantly related to topographic factors such as longitude, latitude and altitude. The high incidence area was mainly concentrated in the valley bell mouth, the valley area of Minjiang River and the Urban heat island.