2021年10月山西一次罕见持续性强降水过程物理机制分析OACSTPCD

The persistent heavy rainstorm that occurred in Shanxi province from October 2th to 7th,2021 was analyzed based on meteorological observation data,NCEP/NCAR 1°×1° reanalysis data,and GDAS data.The findings reveal that the cold air behind the stable Ural low trough and mid-latitude short wave trough moved southward and interacted with the warm moist air outside the subtropical high in southwestern China.Simultaneously,a strong upward movement coupled with high and low-level jets maintained the stability of the low-level shear line and surface convergence line,facilitating continuous transport of low-level water vapor which converged to provide favorable conditions for the occurrence and development of persistent heavy rainfall.The heavy precipitation process can be divided into two stages:convective precipitation and stable precipitation.Although there were significant differences in terms of water vapor source,path,and height between the two stages,water vapor transport from southern Shanxi province dominated as a major contributor throughout both stages.Prior to precipitation onset,symmetric instability was observed in the upper troposphere along with a notable increase in precipitable water content.During the convective precipitation stage,frequent intrusion of dry air established rapid convective instability while cooperation between convergence areas of middle-to-lower tropospheric water vapor and strong updrafts resulted in intense convective weather over Shanxi province.Additionally,local extreme heavy precipitation was further enhanced by blocking effects as well as terrain-induced uplift and contraction.