Abstract:

Abstract The westerly trough is the most precipitation system in central and southern areas of Hebei province, where is the major wheat production area. In order to study the feature of cloud physical structure affected by westerly trough, we analyzed an westerly trough procedure from May 8 to 9 in 2006. It was concluded that: this westerly trough precipitation has thin cloud with dry layer. Observations indicated that the mean moisture content in the cloud is low, with a maximum value of 0.30 g/m3; Shijiazhuang is in the bottom of westerly trough. It is the disadvantage for precipitation; in addition, the low moisture content and the dry layer in the cloud made the cloud droplet and raindrop evaporate, leading the low precipitation of 1 mm in Shijiazhuang.