台风韦森特对季风水汽流的“转运”效应及其对北京“7·21”暴雨的影响  

Long-Range Moisture Alteration of a Typhoon and Its Impact on Beijing Extreme Rainfall

作　　者：徐洪雄[1] 徐祥德[1] 张胜军[1] 付志康[2] 

机构地区：[1]1中国气象科学研究院灾害天气国家重点实验室,北京100081 [2]中国气象局武汉暴雨研究所暴雨监测预警湖北省重点实验室,武汉430074

出　　处：《大气科学》2014年第3期537-550,共14页Chinese Journal of Atmospheric Sciences

基　　金：国家科技支撑计划项目2012BAK10B04;国家自然科学基金重点项目41130960,国家自然科学基金面上项目41075037;国家重点基础研究发展计划项目2009CB421504

摘　　要：2012年7月21日北京地区遭受了61年以来最大的暴雨,造成了大量的人员伤亡与巨大的财产损失。资料综合分析表明台风韦森特在暴雨发生过程中的水汽输送起到"枢纽"的作用,夏季季风通过台风韦森特在副高的影响下将水汽"转运"至暴雨区。为了验证北京异常暴雨过程中台风韦森特的"转运"效应,利用中尺度数值模式WRF对暴雨过程进行数值模拟,结果表明模式能够较好的模拟出此次降水过程的强度、落区,且暴雨发生过程中的水汽输送亦能够较好的再现。通过设计剔除台风的敏感性试验发现,剔除台风韦森特之后降水强度仅为控制试验的50%。进一步分析表明低纬季风水汽气流通过处于东南沿海的台风韦森特向暴雨区域输送水汽,在此过程中西南气流直接向北京区域的水汽输送减少,而西南气流向台风的水汽输送增加,台风与东侧副热带高压之间的偏南气流向暴雨区的水汽输送明显增强,从而印证了上述西南季风气流—台风涡旋—暴雨环流三个系统之间水汽的"转运"效应。以上结果表明远距离暴雨的发生是一个复杂的过程,不仅反映了中低纬度系统的相互作用,而且揭示出夏季季风水汽流对台风涡旋的水汽输送持续供应也可能是台风远距离异常暴雨发生的关键因素之一。Extreme rainfall that occurred in Beijing on July 21, 2012, was the most severe rain event of a 61-year history in that region and caused significant damages. National Centers for Environmental Prediction （NCEP） reanalysis data shows that interaction among Typhoon Vicente, the subtropical high （SH）, and the southwesterly monsoonal flow （SMF） played an important role in this rainfall event. In a process known as the moisture alteration effect of a typhoon, Vicente received moisture from the SMF, which was transported to the Beijing region through the southeasterly flow. To verify this effect, the rainfall event is simulated in this study by using the Weather Research and Forecast （WRF） model withthree nested domains and a finest resolution of 3.33 kin. The control experiments effectively reproduce the distribution and intensity of the rainfall and moisture transport. The results of a sensitivity experiment excluding typhoon Vicente, which is conducted to determine its impact on the extreme rainfall, reveals that approximately 50% of the rainfall can be attributed to the storm. Further analyses of column moisture flux from the sensitivity experiment suggest that more moisture was transported to Beijing through southwest flow that from the southeast. This transport from the southwest to typhoon Vicente and then to Beijing disappeared, which corroborates the moisture alteration effect of the typhoon.

关 键 词：台风远距离 暴雨 水汽输送 季风 

分 类 号：P456[天文地球—大气科学及气象学]