秋季台风“彩虹”引发阳江特大暴雨的成因分析

Causation Analysis of a Yangjiang Extraordinary Rainstorm Triggered by Autumn Typhoon “Mujigae”

利用常规气象观测资料、中尺度自动站资料和NCEP 1°×1°再分析资料,通过诊断方法对强台风"彩虹"引发阳江特大暴雨的成因进行分析,结果表明:阳江特大暴雨是由偏南气流、副高南侧偏东气流、冷空气、地面辐合线及特殊地形共同作用而造成的;偏南气流和偏东气流输送充沛的水汽和不稳定能量,加之持续有冷空气影响和低层辐合,使得阳江降水持续时间长,降雨强度稳定。冷空气的侵入与暖湿气流相互作用,使得最强垂直上升运动出现在阳江地区;同时,冷空气的侵入也降低大气稳定度。阳江不断受地面辐合线影响,加强低层辐合,有利高低空的"抽吸作用",为对流发展提供动力抬升条件。

An extraordinary rainstorm in Yangjiang caused by the strong typhoon ＂Mujigae＂ is analyzed through a diagnostic analysis method by using conventional meteorological data, mesoscale automatic weather stations data and NCEP 1°×1° reanalysis data. The results show that the extraordinary rainstorm is the combined effeet of southerly and easterly airflow from the south of a subtropical high, cold air, a ground convergence line and special topography. Abundant moisture and instability energy are continuously transferred by southerly and easterly airflow, with continuous cold air effect and low-level convergence, whieh make the precipitation in Yangjiang last for long time and rainfall intensity stable. The interactions between the invading cold air and warm air cause the strongest vertical velocity in Yangjiang and reduce atmospheric stability. Due to the constant effect of the ground convergence line, low-level convergence is strengthened in Yanngjiang, and a top-down pumping is induced, providing dynamic lifting conditions for convective development.