Page 182 - 《高原气象》2026年第1期

高 原 气 象 45 卷
178

Structural Characteristics of the Evolution of a Stable Low-motion

Southwest Vortex and Its Relationship with Heavy Rainfall

FAN Dian 1， 2， 3 ， LU Ping 1， 2
（1. Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province， Institute of Tibetan
Plateau Meteorology， China Meteorological Administration， Chengdu 610213， Sichuan， China；
2. Institute of Tibetan Plateau Meteorology， Chinese Academy of Meteorological Sciences， Beijing 100081， China；
3. Gaoping Meteorological Bureau， Nanchong 637100， Sichuan， China）

Abstract： This paper is mainly about the typical stable， low-motion， long-life warm southwest vortex rainstorm
process on July 26-27， 2023. Based on the analytical field data of the Southwest Regional Model （SWC） and the
precipitation data of weather stations， the paper studies the evolution of the horizontal and vertical structure of
the southwest vortex at different stages of its life cycle and its relationship， in terms of space as well as time，
with heavy precipitation. The research results are the following. First of all， there are five distinct stages within
the life circle of the Southwest vortex causing the rainstorm on July 26， 2023： initial， development， peak， main‐
tenance and decay. Secondly， the horizontal and vertical structures of the southwest vortex show asymmetric
characteristics， and the dynamic and thermal structure of the low vortex differ in different evolution stages， thus
affecting differently. In the initial phrase， the release of latent heat of condensation in the convergence uplift en‐
hances the low vortex， and relies more on the transformation of the total potential energy to the kinetic energy，
causing the low vortex to escalate. Since the strong dry cold air moving south weakens the transport of southerly
warm humid wind and vapor， the atmospheric Stratified stability increases， and the low vortex attenuates accord‐
ingly. Finally， the synergistic effect of thermodynamic and dynamic forces is the main cause of the warm vortex
rainstorm. The precipitation at the early stage of vortex development occurs in the warm and wet area around the
vortex center， while that at the strong stage occurs on the side of the strong warm and wet airflow channel， with
the intensity of precipitation corresponding well with that of vortex. Pseudoequivalent potential temperature and
convergence are the key parameters indicating the precipitation area and intensity of the southwest vortex.
Key words： southwest vortex； stable； structure characteristics； rainstorm