一次回流与倒槽共同作用产生的强降雪天气过程分析

Analysis on the Process of Heavy Snowfall Due to the Interaction of Primary Reflux and Trough

本文利用常规天气资料和数值预报产品，应用天气分析和诊断分析方法，对2017年2月21日卢氏县出现的强降雪天气过程的主要影响系统及成因进行分析，最终得出以下结果。①500hPa图上，欧亚高纬地区维持两槽一脊型。从乌山低槽后部不断分裂小股冷空气南下，在高原堆积、加强，与南支槽同位相叠加，使南支槽加深，槽前西南气流加强。地面图上，回流形势与河套倒槽同时强烈发展，两支急流与东路冷空气在卢氏上空交汇，是造成此次强降雪的重要原因。②强烈的水汽辐合和深厚的湿层为此次暴雪天气提供了充足的水汽条件。③低值系统前部的上升运动与喇叭口地形阻挡后产生的上升运动辐合形成深厚的、大范围的、强烈的垂直上升运动是产生强降雪的关键性条件。

In this paper, using conventional weather data and numerical forecast products, using weather analysis and diagnostic analysis methods, the main influence system and causes of the heavy snow- weather process in Lushi Coun- ty in February 21, 2017 were analyzed, and the following results were finally obtained. First, on the 500hPa map, two trough and one ridge type were maintained in the Eurasian high latitude region. From the rear of the low- trough of Wushan, the cold air of small strands was constantly divided into the south, stacked and strengthened in the plateau, superimposed with the same position of the South Branch, making the South Branch deepened, and the southwest air- flow- in the front of the trough was strengthened. On the ground map, the reflux situation and the river sleeve trough were developing at the same time. The two jet and the cold air of the East Road converge over Lushi, which was an im- portant cause of the heavy snowfall. Second, strong water vapor convergence and deep wet layer provided sufficient water vapor conditions for the blizzard weather. Third, the rising motion of the fi＇ont of the low- value system and the rising motion generated by the trumpet topographic obstruction form a deep, large range and strong vertical upward movement, which were the key conditions for the strong snowfall.