螺旋度在一次强沙尘暴天气分析中的应用

Applying of Helicity in Analysis of a Severe Sandstorm

利用NCEP／NCAR每日4次全球再分析网格点资料,对发生在中国西北的一次强沙尘暴进行了螺旋度的诊断分析。结果表明:螺旋度作为强对流天气分析预报中的一个重要物理量,在沙尘暴的预报中同样具有很好的指示意义。沙尘暴区上空螺旋度垂直分布为高层负值,低层正值。高层螺旋度负值的演变与沙尘暴的出现有一定的对应关系。

The helicity of a severe sandstorm happened in Northwest China was analyzed by using global reanalysis grid data of NCEP/NCAR for 4 times a day. As an important physical parameter in analyzing and predicting strong convective weather, the helicity also has good indication in the forecasting of sandstorm. The distribution of helicity over the sandstorm area was negative at higher levels and positive at lower levels. There was definite relationship between the evolvement of helicity's negative value at higher levels and the occurrence of sandstorm. H