宁夏中北部一次暴雪天气过程分析

Analysis of a Snowstorm over the Middle and Northern Ningxia

2009年11月10日08:00—11日14:00,宁夏全区迎来了立冬后第一场雪,降雪量2.0～33.7 mm,其中,吴忠以北普降暴雪,永宁站降雪量(33.7 mm)最大,12 h和24 h降雪量为全区30 a之最。本文利用常规气象资料、宁夏本地化中尺度数值预报(MM5)模式产品,对本次降暴雪的天气环流背景、影响系统及中小尺度系统等进行分析。结果表明:这次中北部暴雪具有明显的中小尺度系统特征。主要影响系统有700 hPa兰州的低涡、偏南气流、地面中β尺度、河套锢囚锋和地面回流,为此次暴雪提供了有利的水汽和动力条件。

The first snow in the winter of 2009 occurred over Ningxiafrom 08：00 on 0th lto 14：00 on 11th November in 2009 and the precipitation was from 2.0 mm to 33.7 mm. The observed biggest snowfall （33.7 mm） in Wuzhong and its north was at Yongning Station, the accumulated precipitation for 12h and 24h was the biggest in the past 30 years. In this paper, the circulation background, influencing systems and meso-scale systems were analyzed by using conventional meteorological data and the outputting products of local meso-scale numerical prediction model MM5 in Ningxia. The results showed that the obvious meso-scale systems caused the snowstorm event, the main influencing systems were Lanzhou vortex at 700 hPa, ground Meso-β-scale systems, Hetao occluded front, south airflow at 700 hPa and the south airflow at the back of ground high pressure provided beneficial vapor and dynamic conditions for the maintaining of snowfall.