太行山中南段暖季极端降水的水汽输送特征

Moisture Transfer Characteristics of Extreme Precipitation During the Warm Season in the Mid-south Section of the Taihang Mountains

利用自动气象站观测降水、ERA5(ECMWF reanalysis version 5)再分析资料和GDAS(Global Data Assimilation System)资料,基于SOMs(self-organizing maps)算法和天气学检验方法,归纳总结2012—2021年太行山中南段75次暖季极端降水事件的环流形势,探讨不同形势下的水汽输送特征及降水差异。结果表明:影响太行山中南段暖季极端降水的环流形势可分为高空槽型、低涡型、副高纬向型、副高经向型和西北气流型5种,其中以高空槽型最为常见,西北气流型最少。低涡型存在孟加拉湾、南海和西北太平洋水汽输送通道,其日降水极值、最大小时降水强度和影响范围在所有类型中均最大,与低涡型相比,高空槽型缺少西北太平洋水汽输送通道,而副高纬向型和副高经向型缺少孟加拉湾水汽输送通道。利用HYSPLIT(hybrid single-particle Lagrangian integrated trajectory)模型追踪气团发现:低涡型和副高纬向型均以来自西北太平洋的水汽输送贡献最大,高空槽型和副高经向型分别以来自黄海沿岸和南海的水汽输送贡献最大。整层水汽收支分析表明:太行山中南段暖季极端降水最主要的水汽流入来自南边界,其他流入边界及各边界水汽流入贡献的相对大小与环流形势有关。

Extreme precipitation events in China have increased significantly in recent decades.Extreme precipitation can easily trigger natural disasters such as urban waterlogging,landslides,and mudslides,which poses a serious threat to the social economy,human lives and property.Currently,research on extreme precipitation has attracted widespread attention.To increase the accuracy of extreme precipitation forecasts,precipitation data from automatic meteorological stations,ERA5 reanalysis data,and Global Data Assimilation System(GDAS)data are used to summarize the synoptic circulation affecting 75 extreme precipitation events in the mid-south section of the Taihang Mountains during the warm season(May-September)for the period of 2012-2021 on the basis of self-organizing maps(SOMs)neural network,synoptic verification method,and hybrid single-particle Lagrangian integrated trajectory(HYSPLIT)model.Characteristics of moisture transfer and the resulting precipitation for various types of synoptic circulation are also discussed.Results show that there are five types of synoptic circulation that affect extreme precipitation during the warm season in the mid-south section of the Taihang Mountains,namely the upper trough type,low vortex type,zonal subtropical high type,meridional subtropical high type,and northwest airflow type.The upper trough type is the most frequent,accounting for 40.0%,while the northwest airflow type is the least common,representing less than 5%.The daily extreme,maximum hourly intensity,and impact range of precipitation resulting from the low vortex circulation are the highest among all types.There are three moisture transfer passages for the low vortex type:The Bay of Bengal,South China Sea,and Northwest Pacific.Compared to the low vortex type,the upper trough type cannot transfer moisture through the Northwest Pacific passage,while neither the zonal subtropical high type nor the meridional subtropical high type can transfer moisture through the Bay of Bengal passage.Air mass tracking results indicate that the contribution of moisture transfer from the Northwest Pacific is the highest for both the low vortex type and the zonal subtropical high type,the contribution of moisture transfer from the Yellow Sea coast is the highest for the upper trough type,and the contribution of moisture transfer from the South China Sea is the highest for the meridional subtropical high type.Analysis of the moisture budget in the whole troposphere reveals that the main moisture inflow of extreme precipitation during the warm season in the mid-south section of the Taihang Mountains comes from the southern boundary.Other inflow boundaries and the relative contribution of all inflow boundaries is related to the synoptic circulation.The moisture budget at the boundaries of the lower troposphere differs from that in the whole troposphere.