大气科学学报2025，Vol.48Issue(1)：62-76,15.DOI:10.13878/j.cnki.dqkxxb.20240924001
中国西北地区复合极端高温-降水事件可能成因
Mechanisms of compound extreme heat-precipitation events in northwestern China
摘要
Abstract
In the context of global warming,the frequency of compound extreme weather and climate events has increased,posing significant challenges to environmental stability and societal resilience.Understanding the mecha-nisms driving these events is crucial for improving their prediction and mitigation.This study examines Compound Extreme Heat-Precipitation Events(CEHPE)in Northwest China,a region frequently impacted by such phenom-ena.The study aims to elucidate the weather-scale dynamics underpinning CEHPE and distinguish them from iso-lated heatwave events to enhance our understanding of these processes. CEHPEs are defined as the occurrence of heavy precipitation within 3 days after the end of a heatwave,ex-cluding instances of heavy precipitation during the heatwave itself.Heatwaves are identified when the DMT ex-ceeds the 90th percentile for at least three consecutive days during summer(June-August).This percentile is cal-culated for each grid cell and each date using a 31-day sliding window based on 30-year baseline period(1961-1990).Heavy precipitation events are defined as daily precipitation exceeding the 95th percentile of precipitation on rainy days(≥0.1 mm/d). The results reveal that CEHPE are triggered by a quasi-barotropic wave train propagating southeastward from upstream regions.When an anticyclonic circulation center approaches the key region(95°-105°E,35°-40°N),a-nomalous descent leads to adiabatic warming,raising lower tropospheric air temperatures.Simultaneously,reduced cloud cover enhances downward shortwave radiation,heating the surface.The heated surface emits more longwave radiation,further warming the lower troposphere and initiating a heatwave.During the heatwave,surface thermal forcing generates a low-level cyclonic circulation anomaly,which directs moisture from the southeast into the key region.The resulting increase in moisture and air temperature enhances atmospheric instability. At the end of the heatwave,when the quasi-barotropic anticyclonic anomaly moves eastward and is succeeded by a cyclonic circulation anomaly,the key region lies west of the upper-level ridge and east of the up-per-level trough.This configuration promotes upper-level divergence,lower-level convergence,and rapid convective development,culminating in extreme precipitation and completing the CEHPE cycle. Mere heatwave events share similar intensity and formation mechanisms with CEHPE.However,in these ca-ses,the quasi-barotropic anticyclonic anomaly expands and weakens but remains centered over the key region,suppressing the development of low-level cyclonic circulation anomalies.Consequently,weaker low-level conver-gence,moisture transport,and atmospheric instability prevent heavy precipitation.Furthermore,the local weakening of the anomalous anticyclone inhibits the approach of upstream cyclonic circulation anomalies,further reducing the likelihood of precipitation. This study elucidates the mechanisms underlying CEHPE in Northwest China and highlights their distinct differences from isolated heatwaves.However,the external forcings contributing to these differences remain unclear and merit further investigation.关键词
复合极端天气和气候事件/热浪/强降水/中国西北Key words
compound extreme weather and climate events/heatwave/heavy precipitation/Northwest China引用本文复制引用
杨怡蓉,袁潮霞..中国西北地区复合极端高温-降水事件可能成因[J].大气科学学报,2025,48(1):62-76,15.基金项目
国家自然科学基金基础科学中心项目(42088101) （42088101）
国家重点研发计划项目(2022YFF0801702) （2022YFF0801702）
