“4.23”特强沙尘暴天气成因分析

为了研究河西走廊特强沙尘暴发生发展机制，利用常规气象资料和美国NECP/NCAR提供的1°×1° 6 h 1次的再分析资料，对2014年4月23—24日发生在甘肃省河西走廊的强沙尘暴天气从气候背景、天气形势、强沙尘暴过程近地面气象要素特征及相关物理量场等方面进行分析。结果表明：强冷空气活动是沙尘暴天气发生的重要原因，沙尘暴天气的发生伴随着地面剧烈降温、气压涌升、风速急增。沙尘暴发生时从低层到高层出现一致的上升运动，垂直上升速度有强到弱的变化与本次沙尘暴从爆发到衰亡的发展过程有很好的对应关系；高空急流中心向低层有明显传播，高空急流核下降是动量下传的重要标志，垂直螺旋度存在着明显的上负下正的特征。沙尘暴发生前，近地层存在逆温层，有利于干对流产生。

Cause Analysis of a Heavy Sandstorm

In order to study the development mechanism of strong sandstorms in Hexi Corridor, according to the conventional meteorological data and data from NECP/NCAR, the authors analyzed the heavy sandstorm which occurred in April 23- 24, 2014 from the perspective of climate background, weather condition, the characteristic of ground meteorological elements of strong sandstorm and related physical factors. The results showed that: the strong cold air activity was an important reason for the sandstorm. The occurrence of sandstorm was accompanied by the dramatic cooling of ground, air pressure surge, and wind speed surge. A consistent upward movement appeared from the lower to the upper level when the sandstorm occurred, the vertical velocity from strong to weak and the sandstorm development process changing from outbreak to decline had a good corresponding relationship. The upper level jet stream center had a significant spread to the lower layer. The descent of the upper jet stream was an important symbol of momentum. There was a marked negative and positive characteristic of the vertical screw. Before the sandstorm occurred, the surface layer had an inversion layer, which was good to produce dry convection.