一次β-中尺度暴风雪的成因及动力热力结构  

A Case Study on Dynamic and Thermal Structures and Mechanism of β-Mesoscale Snowstorm

作　　者：易笑园[1,2] 李泽椿[3] 朱磊磊[2] 孙晓磊[2] 李培彦[4] 

机构地区：[1]南京信息工程大学大气科学学院,江苏南京210044 [2]天津市气象台,天津300074 [3]中国气象局国家气象中心,北京100081 [4]天津气象科学研究所,天津300074

出　　处：《高原气象》2010年第1期175-186,共12页Plateau Meteorology

基　　金：国家科技支撑计划重点项目"城市群高影响天气预报系统的集成和示范"(2008BAC37B01/B05)资助

摘　　要：利用多普勒雷达、地面加密自动站监测资料、常规观测资料、4DVAR雷达风场反演和中尺度数值模式WRF模拟结果,对华北东部一次β-中尺度暴风雪的成因和影响天气系统的热力、动力结构及演变进行了分析。结果表明,(1)造成暴风雪的天气系统是回流形势下的冷锋锢囚锋,其在形成过程、生命史、尺度范围等方面均与温带气旋锢囚锋不同。(2)暴风雪过程分为东路弱冷锋降雪、锢囚降雪、西路强冷锋降雪3个阶段。降雪回波顶高在3～4km,回波强度均在35dBz以下。降雪量集中在锢囚降雪阶段。(3)风廓线(VWP)下层东风层和上层西南风的厚度在降雪各阶段不同,东风急流和西南风急流的变化和配置与降雪量关系密切。锢囚降雪阶段,地面和低层水平风场具有β-中尺度气旋性环流,是造成降雪回波旋转且长时间维持的动力。"人"字状回波的形成是因为风向或风速辐合线的作用。(4)锢囚锋的垂直结构和锢囚过程表明,西路冷锋比东路冷锋陡峭且势力强大,暖湿气团被东西两侧冷锋夹挤、抬升;锢囚时,两侧锋面形成冷式锢囚;锢囚消失时,大风首先在900hPa高度附近出现,进而下传到地面。The composite Doppler radar data, automatic meteorological observing station data and conventional observation data were used to analyze the dynamic and thermal structures and evolution of theβ- mesoscale weather system in west of Bohai Bay, which caused snowstorm on 20~21 December 2008. In addition, the methods of 4DVAR single Doppler radar retrieval and results of mesoscal numerical simulation were used. The results are as followings. Firstly, the occluded cold frontal system under background of cold air returning from east-north area was the weather system caused this snowstorm, which was different from extratropical cyclone occluded frontal in its area, live circle, structure. There are three snowstorm 3 phases including eastern weaker cold front, occluded front and western stronger cold front. Echo top in whole snowfall was under 3 ~ 4 km and reflectivity was below 35 dBz. Snowfall pooled in eddy phase. Secondly, the cyclonic circulation existed on the ground and low level of troposphere, which was help for maintaining of snowing echoes and upward flow. Thirdly, by section-cross of potential pseudo-equivalent temperature and U vector, warm and wet air mass exited and was lifted between east and west cold front. The west cold front was more precipitous than east and two cold fronts formed cold-style occluded frontal system. The transfer of water-vapour from Bohai bay had been existing under 900 hPa levels in live-circle of snowstorm. In return-flow snow phase and eddy phase, another water-vapour belt over 750 hPa levels played important pole on snowstorm. Lastly, with occluded cold frontal system disappearing, strong wind turned up nearby 900 hPa levels and descended at first.

关 键 词：β-中尺度暴雪 冷锋锢囚锋 动力 热力垂直结构 

分 类 号：P426.634[天文地球—大气科学及气象学]