大气科学学报2025，Vol.48Issue(6)：949-961,13.DOI:10.13878/j.cnki.dqkxxb.20241105001
雅鲁藏布江大峡谷区域两类降水过程传播差异成因分析
Formation mechanisms of propagation differences between two types of precipitation systems in the Yarlung Tsangpo Grand Canyon
摘要
Abstract
The southeastern Qinghai-Xizang Plateau is characterized by frequent convective activity.The Yarlung Tsangpo Grand Canyon(YTGC)serves as a key water vapor channel for the plateau,making it crucial to under-stand the evolution of convective systems in this region for improving plateau weather and climate prediction.Pre-vious studies have identified two distinct convective activity zones near 30°N on the plateau;however,convective frequency is notably low directly over the YTGC.Convective systems originating over the western plateau are generally confined west of 95°E,with few propagating eastward.The reason for this frequent inter-ruption of convective activity over the YTGC remains unclear.To address this issue,CLDAS-v2.0 precipitation data were used to analyze 44 summer precipitation events from 1998 to 2019.Based on propagation characteris-tics,the events were classified into two types:"continuous"and"interrupted".The classification revealed a pre-cipitation minimum center over the YTGC,where the eastward propagation of most convective systems is blocked.Only a small subset of systems successfully propagate eastward through the canyon. Because reanalysis data lack sufficient resolution to resolve convective processes under the complex terrain of the plateau's southern slope,high-resolution numerical simulations were conducted.The simulations reproduced both types of precipitation events.Diagnostic analysis showed that the key difference at 500 hPa between the two types lies in the location of convergence:in the"continuous type",the convergence center is located directly o-ver the YTGC,whereas in the"interrupted type"it shifts to higher latitudes.This difference is associated with stronger northerly winds in the"continuous type".Positive pressure kinetic energy eqution diagnosis further indi-cated that anomalous northerlies in the"continuous type"enhance the meridional wind convergence term,in-creasing perturbation kinetic energy and favoring the maintenance and development of convective systems.From a non-equilibrium perspective,the"continuous type"is characterized by a persistent negative divergence tendency zone along the YTGC latitude band,while the"interrupted type"exhibits a transition from negative to positive values from west to east across,creating unfavorable conditions for eastward propagation.Vertical meridional cir-culation analysis revealed that the"continuous type"exhibits a stronger northerly flow,part of which descends a-long the southern slope into the canyon,converges at lower latitudes,and induces upward motion.This ascending branch transports moisture to the mid-levels,where it is carried onto the plateau by southerly winds.Coupled with favorable ascent within the YTGC itself,this process enhances precipitation.A sensitivity experi-ment was further performed by artificially weakening northerly winds in a"continuous"case.The modification caused precipitation over the YTGC to be interrupted,confirming that northerly winds are a crucial factor regula-ting precipitation processes in the canyon region.关键词
雅鲁藏布江大峡谷/对流系统传播/"连续型"和"中断型"/数值模拟Key words
Yarlung Tsangpo grand canyon(YTGC)/convective system propagation/"continuous type"and"interrupted type"/numerical simulation引用本文复制引用
邓一君,陈明诚,葛旭阳..雅鲁藏布江大峡谷区域两类降水过程传播差异成因分析[J].大气科学学报,2025,48(6):949-961,13.基金项目
国家自然科学基金项目(U2342202 （）
42175003) （）
