大尺度低空急流附近的水汽输送与暴雨
投稿时间: 1984-12-13  最后修改时间: 1985-04-22  点此下载全文
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作者单位
朱乾根  
洪永庭  
周军  
中文摘要:本文利用1977—79年华南前汛期的暴雨实验资料,分析研究了大尺度低空急流附近的水汽输送及其对暴雨的贡献。研究表明,与低空急流相联系的暴雨的生成,主要是由于低空急流之下水汽的横向辐合,而不是低空急流所在层的水汽辐合。低空急流之下的水汽由急流左侧向右侧输送,在暴雨区上升,而后在低空急流之上向右侧输送并下沉,从而构成一中尺度的水汽输送环流圈,它与大尺度环流圈同相叠加,有利于暴雨的维持。由于摩擦作用,在低空急流之下的边界层中风向随高度顺转,这是水汽横向输送的主要原因,因此,暴雨可在低空急流左侧的任何位置生成。
 
MOISTURE TRANSFER AND RAINSTORMS AROUND THE LARGE SCALE LOW LEVEL JET STREAM
Abstract:Moisture transfer around the low level jet (LLJ) and its effecton rainstorms are studied. based on thc data of the Heavy Rainfall Experiment over South China during the "early flood"seasons of 1977 to 1979. It is found that development of rainstorms associated with the LLJ is caused mainly by lateral convergence of moisture under the LLJ axis rather than at the same level with the axis. The flow of moisture under the LLJ moves from right to left, as-cends in the storm area, turns right at higher levels above theaxis and then subsides. Thus a meso-scale cell of moisture trans-portation is formed, which is superimposed on the large scalecirculation around the LLJ, a feature favorable for the main-tenance of rainstorms. Winds in the boundary layer under the LLJ veer with altitudedue to friction. This accounts for the lateral transfer of moisture.Hence rainstorms may develop anywhere on the left of the LLJ.
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