大气科学学报2025，Vol.48Issue(5)：828-842,15.DOI:10.13878/j.cnki.dqkxxb.20240530001
华北"23.7"特大暴雨天气尺度系统活动特征及致雨机制
Synoptic-scale system characteristics and mechanisms of the"23.7"extreme rainstorm in North China
摘要
Abstract
From July 29 to August 1,2023,an extreme rainstorm struck North China(hereafter the"23.7"North China rainstorm).The event was characterized by exceptional duration,extensive spatial coverage,and unprece-dented intensity,with multiple historical rainfall records broken.The Haihe River basin experienced its first basin-wide flood since 1963,affecting more than 1 million people.This disaster was ranked as the most significant weather and climate event among China's top ten domestic events of 2023.To investigate the multiscale interaction mechanisms of this extreme event-specifically how synoptic-scale systems mediated the transfer of dynamics and energy from large-scale circulation,organized and sustained mesoscale convective structures,trig-gered localized meso-β/γ-scale activity,and ultimately produced extreme precipitation-we analyzed surface and upper-air observational datasets together with NCEP FNL 1°×1° reanalysis data.Potential function and stream function diagnostics,along with dynamic and thermodynamic analyses,were employed to examine the evolution of synoptic-scale systems and associated variations in moisture,dynamics,and thermodynamics.Key findings in-clude:1)A"chain-like"configuration formed among the tropical monsoon system,the residual circulation of Ty-phoon Doksuri,and the subtropical high.The northward movement of Doksuri's remnant low established a trans-continental moisture corridor from eastern China to North China,sustaining anomalously strong water vapor trans-port from the tropical Indian Ocean,South China Sea,and Northwest Pacific.This unprecedented moisture conver-gence provided critical conditions for extreme precipitation.2)Synoptic-scale systems exerted pivotal control through adjustments of mid-to high-latitude upper-level circulation,particularly variations in the position and in-tensity of the westerly jet.These changes enhanced anticyclonic vorticity and upper-level divergence over North China,inducing"high-level suction"that propagated upward motion downward into the lower troposphere.Cou-pled with cyclonic convergence generated by southeastern low-level jets,this vertical circulation reinforced deep convection across the region. The role of diabatic heating was further examined using the apparent heat source Q1 and moisture sink Q2.Combined with full-form vorticity,vertical velocity,and potential tendency equations,diagnostics revealed that substantial diabatic heating during the rainfall process provided strong positive feedback,intensifying the vertical dynamic structure of the rainstorm system and deepening the geopotential height anomalies over North China.This feedback further strengthened the precipitation environment,sustaining the prolonged and intense rainfall.Overall,the rainstorm was dynamically driven,with thermal processes providing secondary reinforcement. This study demonstrates that the"23.7"North China rainstorm exhibited distinct synoptic-scale dynamic-thermodynamic mechanisms compared to historical events.While resembling CISK-like processes,initiation oc-curred aloft,with anticyclonic divergence from the westerly jet triggering mid-level convection.Subsequent en-hancement of low-level convergence by a jet-trough interaction activated lower-tropospheric convection,leading to vertical coupling of cumulus activity that reinforced the rainfall environment across North China.Unlike classical CISK,where boundary-layer frictional convergence initiates convection,this event was initiated by upper-tropospheric forcing.From a scale-interaction perspective,the stable coupling of upper-and lower-level jets differed from mechanisms observed in the 2012 Beijing"7.21"rainstorm or the 1996 North China event.Although sharing large-scale circulation similarities with the 2021 Henan rainstorm,the"21.7"event differed in emphasizing mid-lower tropospheric dual-jet and latent heat dynamics.These mechanistic differences explain the extreme features of the"23.7"event,including its broader spatial extent,larger cumulative rainfall,stronger hourly intensity,and prolonged duration.关键词
华北暴雨/天气尺度/非绝热加热/致雨机制Key words
heavy rainfall in North China/synoptic scale/diabatic heating/rainmaking mechanism引用本文复制引用
李峰,吴蕾,张林,邵长亮,蒋建莹..华北"23.7"特大暴雨天气尺度系统活动特征及致雨机制[J].大气科学学报,2025,48(5):828-842,15.基金项目
国家自然科学基金项目(U2342216) （U2342216）
自然资源部空间海洋遥感与应用重点实验室开放课题(202402001) （202402001）
北极阁基金项目(BJG202203) （BJG202203）
