青藏高原东南角“桃花汛”暴雨的天气学成因及地形影响机制研究

青藏高原东南角(滇西北、藏东南)2-4月降水比夏季多,大雨暴雨频繁出现,这一多雨特征俗称“桃花汛”。在当地山高谷深的复杂地形下,暴雨往往导致洪涝、滑坡泥石流灾害,严重制约当地经济发展和边疆稳定。目前这种降水产生的机制仍不清楚。本项目以“桃花汛暴雨”(以下称暴雨)形成的天气学成因及地形影响机制为聚焦点,利用各种观测资料和高分辨地形及数值模拟资料,研究暴雨形成的原因.通过资料分析、动力诊断、数值模拟等方法,重点研究(1)天气系统及其配置和环境参数对暴雨发生的作用(2)暴雨的水汽来源、输送特征及短时集中与抬升机制(3)地形影响造成暴雨的中尺度系统的数值模拟分析及敏感性试验,分析地形涡旋、地形辐合线、地形重力波等中尺度系统对暴雨的作用。通过阐明各种天气系统对暴雨的贡献及刻画水汽输送和地形作用造成水汽集中与抬升特征,建立造成暴雨的各种天气系统配置的概念模型.为暴雨预报提供科学思路和预报着眼点。

In the southeast corner of the Tibet Plateau (Northwest Yunnan and Southeast Tibet), there is more precipitation from February to April than that in summer, with frequent heavy rains and rainstorms in this period of time, which is known as "spring flood" or literally “peach blossom flood” in Chinese . The terrain of the southeast corner of the Tibetan Plateau is complex and unique, and the spring flood often leads to flood and debris flow disasters, which can seriously restrict the local economic development and the stability of Yunnan’s frontier. However, the mechanism of this kind of precipitation is still unclear. This project focuses on the synoptic causes and topographic effect on "torrential rain of the spring flood" (hereinafter referred to as "torrential rain") and studies the causes of torrential rain by using various observational data, high-resolution terrain and numerical simulation data. Through data analysis, dynamic diagnosis and numerical simulation, it focuses on: (1) the influences of synoptic systems and their configuration as well as the environmental parameters on the occurrence of torrential rain; (2) vapor source, characteristics of water vapor transport and the mechanism of short-term concentration and uplift of moisture contributing to the torrential rain; (3) numerical simulation and sensitivity test of mesoscale systems of torrential rain caused by topographic effect, investigating the effect of mesoscale systems such as vortex, convergence line and gravity wave forced by the terrain. By clarifying the contributions of different scale weather systems to torrential rain and depicting the physical picture of the water vapor transport and topographic effect on water vapor concentration and uplift, a novel conceptual model of multi-scale synoptic system configuration will be established, providing clues for the forecast of the torrential rains.