北京一次冬季回流暴雪天气过程的数值分析  

Numerical Simulation and Analysis on a Heavy Snow of Return-Flow Events in Beijing

作　　者：李青春[1] 程丛兰[1] 高华[1] 丁海燕[1] 

机构地区：[1]中国气象局北京城市气象研究所,北京100089

出　　处：《气象》2011年第11期1380-1388,共9页Meteorological Monthly

基　　金：中央公益性科研院所基本科研业务费专项(IUMKY201002)资助

摘　　要：回流天气是华北地区冬、春、秋季节产生降雨(雪)的主要天气类型,预报员常常因对回流天气系统结构特征认识不足和诊断失误而导致预报的失败,是降雨(雪)预报的难点和重点。利用北京地区高分辨率快速循环同化中尺度数值预报系统(BJ-RUC)对2010年1月2—3日一次典型的回流暴雪天气过程进行模拟,分析数值模式的模拟能力,研究各层主要影响系统结构特征及形成暴雪的关键性条件,探讨典型回流暴雪天气过程的形成机理。主要结论为:数值模式对此次暴雪过程的近地面回流冷空气、中低层低值系统及变化特征、主要降雪时段和降雪量模拟效果较好,对降雪落区的模拟存在一定偏差。低层回流偏东风遇到地形后引起垂直运动主要在低层800 hPa以下,所产生的降雪量不大,而其与上游850～700 hPa低涡系统发展东移其前部的上升运动汇合所形成的大范围、深厚、强烈的上升运动是产生明显降雪的关键性条件。上游低涡系统前部西南暖湿气流相对应的大湿度区移近是产生较强降雪的重要条件。持续的低层回流冷空气湿度较大,对于低层大气起到水汽输送的作用。回流冷空气使低层大气维持长时间的水汽输送并与其上层东移的大湿度区相结合,增加湿层厚度,有利于降雪持续而形成较强降雪。降雪开始时间和降雪强度的变化与对流层中下转偏南风的时间和偏南风风速增大有关。The typical return-flow events with heavy snow during 2—3 January,2010 by using Beijing local high-resolution rapid update cycle mesoscale model system（BJ-RUC） are simulated.The characteristics of synoptic system in each layer and key snowfall factor are analyzed.The results show that the BJ-RUC model can well simulate the snowfall distribution,position and time change,and the main situations of heavy snowfall which are caused by the cold air return-flow in the low-level,and the 850—700 hPa layer low-vortex system.But the snowfall center has still some deficiency.When the vertical ascending motion is produced in lower atmosphere by the cold return-flow encountering terrain,the snowfall is not high. During the snowfall,the dynamic lifting which is caused by the cold return-flow combining with the ascending motion of the foreside of low vortex,forms a deeply and violent ascending motion,that is the key factor to cause the heavy snow.The durative and cold return-flow with high humidity transports water vapor in the lower atmosphere.The humidity in the lower-mid troposphere is increased by the southwestern air flow.The return-flow increases thickness of wet-layer,reaching above 600 hPa.It plays an important role in producing the heavy snow.The start and intensity of snow fall are related to the moment of the direction change to southern wind and the south wind speed.

关 键 词：暴雪 回流 快速循环数值预报系统RUC 数值模拟 

分 类 号：P457.2[天文地球—大气科学及气象学]