Abstract:

The strongest cold wave weather occurred on Ap ril 19 to 20 of 2008 in Hexi Corridorwhich influenced by the strong cold air
moving southeastward from West Siberia. The circulation situation evolvement characteristc of thisweather eventwas analysed based on
Micap s data, six hours reanalysis data ( horizontal resolution 2. 5°×2. 5°) from NCEP /NCAR. The 300 hPa high - level jet stream,
500 hPa vorticity, temperature advection and vertical velocity, 700 hPa water vapor flux divergence from 08: 00 Ap ril 15 to 08: 00 Ap ril
20 (60 - 105°E, 35 - 60°N) were caculated. The results show that the onset of the cold wave was related to high - level jet moving
southeastward and strengthening gradually, and the positive vorticity area at 500 hPa was in accord with the frontal zone in front of
trough, which was benefit to the strongest cold airmoving southeastward. The low - levelwater vapor flux divergence distribution influenced precipitation obviously under the cold wave weather condition, rainfall occurred in the area of the minimum value ofwater vapor
flux divergence, and no rainfall but dustweather occurred in the area of the maximum value.

Key words: strong cold wave, case, diagnosis

摘要：

2008年4月19～20日,受西伯利亚东移南下的强冷空气影响,河西地区出现了自2001年以来最强的1次寒潮天气。利用M ICAPS资料分析了这次强寒潮爆发时的环流形势演变特征。同时采用NCEP /NCAR 2. 5°×2. 5°每天4次再分析资料,计算了60～105°E、35～60°N区域内, 4月15日08时～20日08时300 hPa高空急流, 500 hPa涡度、温度平流、垂直速度, 700 hPa水汽通量散度等物理量。结果表明:此次强寒潮的爆发与高空急流在东移南下过程中逐渐加强有关, 500 hPa正涡度区与槽前锋区配合一致,更有利于引导强冷空气东移南下。低层强冷平流对地面加压降温作用至关重要,垂直速度与大气层结稳定度有关。700 hPa水汽通量散度场分布特征对寒潮天气条件下的降水形成有明显影响,水汽通量散度极小值区域均有降水,最大值区域无降水而有沙尘天气。

关键词: :强寒潮, 个例, 诊断