四川地区短时强降水事件时空演变特征研究

利用四川地区自动气象站逐小时降水观测资料，分析了2010~2019年5~9月短时强降水事件24h累计降水量、频次和强度的时空分布特征，探讨了短时强降水事件发生的频次、极值分布及其与地形、海拔高度等的关系。结果表明:四川地区平均24h累计降雨量基本在50mm以上，盆地东北部、西南部、南部及阿坝州东部甚至超过100mm，最大值出现在广安，达175mm。四川地区短时强降水事件开始时间的日变化特征表现为“V”型结构的夜间峰值位相，事件持续时段多为傍晚至凌晨，时长可达10h以上，最长甚至可持续22h。在强降水事件极值的日变化上，极大值频次和降水量呈单峰结构，在03时达到最大，其后逐渐减小至15时达到谷值，而后再次增大；降水强度呈弱双峰结构，分别在04时和16时达到谷值，13时和18时达到峰值，其日变化呈“增-减-增-减”的特征。四川短时强降水事件与复杂地形有密切的关系，5~6月事件活跃区在四川盆地中部，7月在盆地西部的龙门山脉一带，8月在雅安、乐山附近，9月在盆地北部且频次明显减少；短时强降水事件的最大小时雨强可达80mm以上，出现在7~8月的盆地西部龙门山一带和南部地区。短时强降水事件随着海拔高度的增加，发生频次和日数逐渐减少，海拔2000m以上地区基本无强降水发生日出现( 峨眉山气象站例外)。 

Temporal and Spatial Evolution Characteristics of the Short-Duration Strong Rainfalll Events in Sichuan

Using the hourly precipitation observation data of automatic weather stations in Sichuan Province, the spatial and temporal distribution characteristics of 24-hour cumulative precipitation, frequency and intensity of short-term rainfall events during the main flood season （May -September) from 2010 to 2019 were analyzed. The frequency and extreme value distribution of short-term heavy rainfall events and their relationship with topography and altitude were discussed. The results show that the average 24-hour cumulative rainfall in Sichuan is basically more than 50mm, the northeast, southwest and south part of Sichuan Basin, and eastern Aba Prefecture exceed 100mm. The maximum is in Guang'an, reaching 175mm. The diurnal variation of the short-term heavy precipitation event in Sichuan area is manifested as a “V”-shaped structure of the peak phase at night. The event duration is mostly from evening to early morning, and the duration can be more than 10 hours, and last up to 22 hours. In the daily variation of extreme values of heavy precipitation events, the maximum frequency and precipitation showed a unimodal structure, and reached the maximum at 03: 00, and then gradually decreased to the valley at 15: 00, and then increased again. The precipitation intensity of the event showed an insignificant double-peak structure, reaching the valley values at 04: 00 and 16: 00, and reaching the peak values at 13: 00 and 18: 00. The diurnal changes showed a trend of first increasing and then decreasing, then increasing and then gradually decreasing. Short-term heavy precipitation events in Sichuan are closely related to the complex topography of the area. The active area of events are in the central Sichuan Basin from May to June, and in the Longmen Mountains in the western Sichuan Basin in July, near Ya'an and Leshan in August, and in the northern Sichuan Basin in September. The maximum hourly rainfall intensity of short-term heavy rainfall events can reach more than 80 mm, which occurs in the Longmen Mountains in the western basin and the southern region from July to August. With the increase of altitude, the frequency and days of short-term heavy rainfall events decreased gradually, and there was almost no heavy rainfall occurred in areas above 2000m ( except Emeishan weather station ).