西南地区东部区域性暴雨事件的客观识别及其变化特征

Objective Identification and Variation Characteristics of Regional Heavy Rainfall Events in the East of Southwestern China

利用区域性极端事件客观识别方法(OITREE)和1961-2018年西南地区东部118站逐日降水资料对该区域近58年的区域性暴雨事件进行了识别,确定了相应的OITREE方法的参数组,共识别得出246次区域性暴雨事件,其中25次达到极端强度,2004年9月3-6日发生的区域性暴雨事件是西南地区东部近58年来综合强度最强的一次区域性暴雨事件。进一步分析表明:西南地区东部区域性暴雨事件的持续时间主要为2天,最长为5天;事件的累积强度集中在500~1000 mm之间,累积面积集中在10×10^(4)~20×10^(4) km^(2)。西南地区东部区域性暴雨事件多发于5-9月,其中7月最多,占总发生频次的31.7%。四川东部和重庆西部的平原区是暴雨事件的频发和强度中心地区。近58年西南地区东部持续性区域暴雨事件增多[0.57次·(10a)^(-1)],持续时间延长[1.2 d·(10a)^(-1)],最大影响范围扩大[5.7×10^(4) km^(2)·(10a)^(-1)],极端强度也增强[73.4 mm·(10a)^(-1)]。

The regional heavy rainfall events(RHREs)were identified by using the Objective Identification Technique for Regional Extreme Events(OITREE)based on the daily precipitation data of 118 stations in eastern Southwest China(ESWC)from 1961 to 2018.The parameters related to OITREE method were determined.There are 246 RHREs in total in the ESWC from 1951 to 2018,of which 25 are extreme RHREs.The strongest RHRE occurred on 3-6 September 2004,detected by the comprehensive intensity.Further analysis shows that the duration of the RHREs in the ESWC is generally 2 days and the longest duration is 5 days.The cumulative intensity of RHREs is about 500~1000 mm,and the cumulative area is about 10×10^(4)~20×10^(4) km^(2).RHREs in the ESWC occur frequently from May to September,with the highest frequency of the RHREs in July,accounting for 31.7%of the total occurrence frequency.The plain areas in eastern Sichuan and western Chongqing are the center areas with the highest frequency and intensity of RHREs.During the past 58 years,the number of persistent RHREs in the ESWC shows a significant increasing trend at the rate of 0.57 times per decade.Also,the duration,the maximum impacted area and the extreme precipitation of the RHREs are all show a significant increasing trend at the rate of 1.2 d·(10a)^(-1),5.7×10^(4) km^(2)·(10a)^(-1) and 73.4 mm·(10a)^(-1),respectively.