“14.4.23”河西走廊特强沙尘暴演变过程特征分析  

Characteristic Analysis of the "2014.4.23" Strong Sandstorm's Evolution Process in Hexi Corridor

作　　者：钱莉[1,2] 滕杰 胡津革 

机构地区：[1]中国气象局兰州干旱气象研究所甘肃省(中国气象局)干旱气候变化与减灾重点(开放)实验室,甘肃730020 [2]甘肃省武威市气象局,武威733000

出　　处：《气象》2015年第6期745-754,共10页Meteorological Monthly

基　　金：国家自然科学基金项目(41275118)资助

摘　　要：利用常规气象观测资料和ECMWF数值预报产品,对2014年4月23日甘肃河西走廊发生的特强沙尘暴过程形成和减弱原因进行天气动力学诊断分析,结果表明:500 hPa乌拉尔山脊前不稳定槽强烈发展,极地强冷空气向南爆发是这次特强沙尘暴产生的大尺度触发系统,地面冷锋所带来的强风是产生特强沙尘暴的主要原因。特强沙尘暴在河西走廊中西部增强的原因:700~850 hPa河西走廊近乎中性的温度层结,加上强冷平流和低空急流,有利于锋生和动量下传;地面冷锋强变压、变温梯度及日变化促使沙尘暴在河西西部爆发性发展。河西走廊中西部低空强上升运动有利于增大近地面沙尘浓度;强烈的温度差动平流和垂直风切变,加大了热力和动力不稳定。特强沙尘暴在河西走廊东部减弱的原因:造成特强沙尘暴的天气系统在河西东部北行减弱及河西走廊狭管效应地形环境消失;午夜日变化造成锋消;前期持续阴雨天气,使疏松裸露的地表土壤和沙漠形成一层板结层,增加起沙难度。Based on conventional observation data and ECMWF numerical forecast products,dynamic diagnostic analysis was carried out to find out the causes for the formation and weakening of sandstorms that happened in the Hexi Corridor of Gansu Province on 23 April 2014.The results showed that unstable trough develops strongly in front of the ridge of Mountain Ural at 500 hPa,steering strong cold air from the North Pole to move southward quickly,which is the large-scale system leading to the sandstorm.And strong storms accompanying the surface cold front is the main cause for the outbreak of the severe sandstorm.The reason why the strong sandstorm gets enhanced in the Midwest of the Hexi Corridor is that nearly neutral temperature stratification in 700 — 850 hPa coupled with strong cold temperature advection and low-level jet of Hexi Corridor is conducive to the frontogenesis and downstream of momentum.The strong pressure gradient,temperature gradient and daily variation before and after the cold front causes explosive development of sandstorm in the eastern part of Hexi Corridor.In addition,the strong upward motion of low altitude near the Midwest of Hexi Corridor is in favor of increasing dust concentration.Strong differential temperature advection and vertical wind shear enhance thermal and dynamic instability.The reason why strong sandstorm weakens in eastern part of the Hexi Corridor is that the main weather system resulting in the strong sandstorm weakens and moves northerly,and the narrow tube effect disappears in the eastern part of Hexi Corridor.Besides,the diurnal change of temperature and pressure gradients at midnight lead to frontolysis.Even the rainy weather continues in the early stage so that the exposed surface soil becomes loose and deserts form a compacted layer to increase the difficulty of raising sand.

关 键 词：特强沙尘暴 发生机制 诊断分析 物理量特征 

分 类 号：P425.55[天文地球—大气科学及气象学]