咸阳市“８·１４”与“８·８”两次大暴雨天气对比分析

利用常规观测资料及FY-2C气象卫星云图等非常规观测资料，从环流背景、水汽条件、触发机制、不稳定能量等方面，对2009年7月7日-8日汾阳市久早转大雨天气过程进行了综合分析。结果表明：此次久旱转大雨天气出现在中纬度环流经向度加大和副高西进北抬的形势下；500hPa高空槽东移引导西南涡东移北上，是造成此次大雨过程的直接原因；对流云团TBB值越大，对应的降水强度越强；低空西南风急流的建立打通了水汽北上的通道，为强降水发生提供了有利条件；低层不稳定，高层稳定的能量结构对强降水的发生十分有利；强烈的垂直上升运动为汾阳大雨天气提供了有利的动力抬升机制。

Analysis of A Typical Transition Weather in Fenyang City, Shanxi Province

Based on conventional ohservational data, FY-2c meteorological satellite image data and other unconventional observational data, the process of the weather conditions from drought to heavy rainfall in Fenyang city in July 7th to 8th 2009 is analyzed. The resuhs show that： the direct factors for the change were the eastward upper trough at 500 hPa layer guides vortex to north-east which is made the subtropical high turn suddenly to the nnrth-west under the feature of middle latitude circulation which The TBB of convective clouds was higher and the intensity of precipitation was stronger. It provided a favorable condition for strong precipitation that low-level southwest jet provided a vapor channel. It was beneficial for heavy precipitation that low-level was instability and the energy structure in high-level was stable. Strong vertical ascending motion provided favorable mechanism for heavy precipitation which occurred in FenYang Citv