南四湖地区一次农业致灾天气成因分析

Analysis of an Agricultural Disaster Caused by Weather in Nansi Lake Area

为了提高南四湖地区灾害性天气预报预警技术能力和水平,笔者对2012年9月19日发生在山东西南部南四湖地区附近的一次造成农业灾害的雷雨大风、冰雹天气过程进行了诊断分析。结果表明:上干冷、下暖湿的层结结构特点的前倾槽,对本次强对流天气的发生十分有利。前倾槽槽后的干冷空气入侵作用,为强对流的产生提供了激发机制。地面图上强风向辐合中心更加容易触发强对流天气。K指数的大值中心移动方向与强降水的移动方向基本一致。对流层高低层存在的风向风速的垂直切变,有利于强对流性风暴发生、发展。0℃层和-20℃层高度差较小时,有利于冰雹的形成。组合反射率因子和回波顶高等雷达产品对冰雹发生的区域有一定的指示作用。

The paper aims to improve severe weather forecasting and warning technology in the Nansi Lakearea. The author analyzed an agricultural disaster caused by thunderstorm winds and hail in September 19,2012 in Nansi Lake area which located in the southwestern Shandong Province. The results showed that thefavorable condition for the occurrence of severe convective weather was the forward-tilling trough in which thedry and cold air was above the moist and warm air. The dry and cold intrusion which was behind the trough wasthe trigger mechanism of the strong convection. Strong wind convergence center easily triggered severeconvective weather on the ground. A movement direction of the maximum center of K index was consistent withthe direction of movement of heavy rainfall. The wind vertical shear of the direction and speed on tropospherewere conducive to strong convective storm development. An appropriate height between 0℃ layer and-20℃layer was conducive to the formation of hail. Composite reflectivity factor and echo tops had certain indicationfor the region of the hail.