2013年春季宁夏一次强沙尘天气成因分析

An Analysis of Causes of a Strong Dust Weather in Spring of 2013 in Ningxia

应用2013年4月17日宁夏强沙尘天气过程各站实况观测资料、MICAPS提供的相关资料、NCAR/NCEP再分析资料,分析了2013年春季大风沙尘天气的成因、层结状态特征、以及涡度、散度、垂直速度和温度平流等物理量场特征。结果表明:本次大风沙尘天气是东北冷涡南压、蒙古横槽南摆转竖和动量下传综合作用下产生的,700 hpa中高层有强冷平流影响宁夏;地面气象要素反映沙尘暴发生前气压、相对湿度降到这一天的谷底,而气温上升至当日最高,在强的热低压梯度和冷锋的作用下产生大风;散度场与垂直速度场相互配合,低空辐合高空辐散有利于气流上升,为大风、沙尘天气的发展提供了动力条件.

The causes and the stratification characteristics of the gale sand dust weather in the spring of 2013 as well as the physical quantity field characteristics such as the vorticity, divergence, vertical velocity and the temperature advection, were analyzed using the observation data on the strong dust storm weather process in April 17, 2013 in Ningxia, at various sta-tions, the relevant data provided by the MICAPS and the reanalysis data of NCAR/NCEP. The results showed that the gale sand dust weather were caused by the comprehensive effects of the northeast cold vortex southward, the Mongolia trough swinging southward and turning the vertical and the momentum transferring. The strong cold advection in the 700 hpa mid-dle and high level affected Ningxia. The surface meteorological elements reflected that the air pressure and the relative hu-midity fell to the bottom of the day before the gale sand dust weather,but the temperature rose to the highest,the big wind were caused by the effects of cold front and the strong thermal pressure gradient. The divergence field and vertical velocity field cooperated with each other, the low level convergence and the upper divergence helped the increasing of flow. And it provided the dynamic conditions for the development of wind, and sand dust weather.