一次强沙尘暴天气的成因分析

Analysis on Formation of a Severe Sandstorm Weather

利用常规观测资料和NCEP/NCAR再分析资料以及MM5模拟结果,对2006年3月27日发生在河北省南部邢台、邯郸等地的一次强沙尘暴天气过程进行分析,结果表明,强沙尘暴天气是由高空横槽和地面冷锋后西北大风引起的,高空急流的加强及中尺度反环流圈的形成,促使高层动量下传到地面则是强沙尘暴发生的另一个重要原因;低层螺旋度正值中心变化对强沙尘暴预报有一定的指示作用;沙尘暴区始终位于低层螺旋度正的极大值中心南侧,沙尘暴爆发时,沙尘暴区上空螺旋度值出现次大值中心,随着螺旋度中心值增大沙尘暴强度增强。

A severe sandstorm weather befell in the south of Hebei Province on 27 March 2006. The authors use routine meteorological data and reanalysis grid data of NCEP/NCAR and the model products of MM5 to analyze the circulation background and the physical mechanism of this weather phenomenon. The results show that the severe sand storm process is formed by the upper air trough and the northwest gale behind the clod front. The enhancement of upper jet and the forming of mesoscale counter-circulation lead to the momentum downward-transporting from high level to the ground. The variation of the positive helicity center in low level has indicating significance for forecasting sandstorm weather. The weather of sandstorm always occurred in the areas at south side of the positive helicity center. There was secondary largest helicity center over the sandstorm area, and the intensity of sandstorm increased along with the increase of the helicity center value.