北京地区两次极端特大暴雨过程中短时强降水环境条件对比分析  

Comparison of short-duration heavy rainfall environmental conditions during two extreme torrential rainfall events over Beijing area

作　　者：田付友 杨舒楠 郑永光 夏坤[2] TIAN Fuyou;YANG Shu'nan;ZHENG Yongguang;XIA Kun(National Meteorological Center,Beijing 100081;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029)

机构地区：[1]国家气象中心,北京100081 [2]中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室,北京100029

出　　处：《暴雨灾害》2021年第1期27-36,共10页Torrential Rain and Disasters

基　　金：国家重点研发计划(2017YFC1502003,2018YFC1507504);国家重点基础研究发展计划(2015CB954101)。

摘　　要：针对北京地区2012年7月21日(简称“7.21”过程)和2016年7月20日(简称“7.20”过程)极端特大暴雨中的短时强降水,对短时强降水实况、环流形势、地形影响及环境的动力、水汽和热力条件进行了分析,并结合较长时段的历史资料,从单点和区域角度对环境动力、水汽和潜在热力条件的极端性进行了对比分析。结果表明:(1)尽管两次过程中的短时强降水实况差异显著,但均出现在非常有利的天气形势下。(2)针对短时强降水环境的单点动力、水汽和热力条件对比显示,两次过程中的850 hPa动力抬升和整层可降水量(PWAT)均极端偏强,但抬升指数(LI)表征的热力条件差异差别巨大,2012年“7.21”过程中为偏强,2016年“7.20”过程中为偏弱。(3)针对长时间序列资料的标准化偏差异常(SD)显示,两次过程中850 hPa风场和PWAT的SD均超过了3σ,为极端偏强,LI表征的潜在热力条件方面,2012年“7.21”过程中低于-1σ,2016年“7.20”过程中与历史同期持平,表明热力条件的差异是导致两次极端暴雨过程中短时强降水强度巨大差异的重要原因。The short-duration heavy rainfall observations,the synoptic patterns,the terrain effects,and the environmental conditions for short-duration heavy rainfall occurred during the two extreme torrential rainfall events of 21 July 2012(shortly for“7.21”)and 20 July 2016(shortly for“7.20”)are analyzed.The extremity of environmental low level forcing,moisture content,and instability are studied from point and regional perspectives by comparing with long time series data.Results indicate the following.(1)Though remarkable difference in the short-duration heavy rainfall observations,both events happened under favorable synoptic patterns.(2)Comparison of environmental conditions with long time series reference at point and regional scale shows that the short-duration heavy rainfall happened under extremely strong low level forcing and strong precipitable water of the whole layer(PWAT)environments,but significant difference for the instability represented by lifted index(LI).The LI during“7.21”is much stronger while during“7.20”is weaker than that for the reference.(3)The standard anomalies(SD)of environmental conditions with long time series data show that the 850 hPa wind field and PWAT during both events are greater than 3σ,indicating low level forcing and moisture content are very strong.But for latent instability indicated by LI,the SD during“7.21”is-1σ,while no remarkable SD obtained during“7.20”.The difference of latent instability is one of the important reasons causing the great difference on intensities of short-duration heavy rainfall during the two events.

关 键 词：极端暴雨 短时强降水 环境条件 对比分析 

分 类 号：PP458.121.1