四川盆地夏季区域性极端降水事件特征及其成因

Characteristics and Causes of Regional Extreme Precipitation Events in Summer Over Sichuan Basin

利用四川盆地1981-2015年夏季102个气象台站逐日降水资料, NCEP/NCAR逐日再分析资料,分析了四川盆地区域性降水及极端降水事件的时空特征,对极端降水事件发生的环流场进行合成分析,讨论其环流异常特征.研究表明:近35年四川盆地总降水量及夏季降水量时空变化特征较为一致;盆地夏季区域性极端日降水量的99%分位阈值为40.5 mm/d, 2005年开始极端日降水事件明显增多,区域性极端降水事件多发于7月下旬以及8月中旬;极端日降水事件呈现低层辐合、高层辐散的环流结构;端日降水事件的形成与四川盆地的大气净加热以及周边大范围地区的净冷却形成的加热场异常梯度有关.

The daily precipitation data over Sichuan Basin and daily NCEP/NCAR reanalysis data of 102 meteorological stations are used to analyze the spatio-temporal characteristics of regional precipitation events and extreme precipitation events, analyze the circulation fields of the extreme precipitation events and discuss their anomalous characteristics of circulation. The results show that the spatio-temporal characteristics of total precipitation amount and summertime precipitation are fairly consistent in the recent 35 years;the threshold of the precipitation amount of daily precipitation extreme events is 40.5 mm/d on the 99th percentile, extreme daily precipitation has increased significantly since 2005, and the daily precipitation extreme events tend to occur from late July to mid-August more frequently;its circulation structure shows convergence of low level and divergence of high level;and the formation of daily extreme events is related to the atmospheric net heating over Sichuan Basin and the anomalous gradient of the heating field formed by the net cooling of the surrounding areas.