山东一次飑线过程的中尺度分析

2005年7月12日山东中西部地区发生了一次飑线天气过程.利用自动气象站、多普勒雷达及NCEP 1°×1°的逐6小时资料,从天气形势、垂直结构、地面中尺度场等角度分析了该飑线过程.结果表明:低涡后部的横槽转竖是这次飑线发生的大尺度环流背景,横槽转竖过程中引导高空冷空气下泻,形成上干下暖的不稳定层结,不稳定层结主要是通过高低空的温度差动效应来实现.与飑线相对应的是一支强盛的上升气流,飑线后部是下沉气流,具有较高动量的高空气流下沉至地面向外辐散,使得飑线后部地面辐散区中的风场大大加强.地面辐合带的走向和摆动对飑线移动有明显影响,辐合强度不断增强和范围不断扩大之后,天气也就愈激烈.地面低压区的移近、合并,有利于形成强对流发展的环境场.

Mesoscale Analysis of a Squall Line Affecting Shandong Province

Based on the automatic meteorological station, Doppler radar and NCEP reanalysis data of 1°×1° with 6 h interval, a squall line weather event on July 12, 2005 was analyzed. This severe convection occurred under the background of traverse trough developing into vertical trough. When a traverse trough turned into vertical trough, the cold air pours from high altitudes, thus an instable stratification with upper layer dry and lower layer wet was formed, which was carried out by high low differential effects of temperature. There was a strong upward airflow before squall line and a falling airflow with large momentum behind it. The surface wind behind squall line strengthened by relatively strong momentum transmitted from high to low. When squall line promulgated, old convergence line split or united, so new convergence line came into being consequently. When surface convergence intensity became stronger, convective weather became more severe. Severe weather was located behind disturbed convergence center. The convergence center was situated behind disturbed low pressure band and the high pressure stood before divergence center. There was a low pressure dangled after high pressure, and mesoscale high or low pressure indicated a foreboding of convective weather.