暴雨过程大尺度热量、水汽和动量收支分析

近年来对长江流域梅雨期热源热汇分布的一些研究1]-3]表明,热源热汇的分布和梅雨期降水性质存在着年际变化,同时,研究区域不同,天气形势和时空尺度不同,所得各类收支的垂直分布特征亦有较大差别。本文用曲面拟合方法计算了1989年梅雨期6月27日至7月4日江南地区暴雨过程的时空平均热量、水汽和动量收支,得到的垂直分布特征是:(1)加热率Q₁峰值位于400—500百帕气层,减湿率Q₂峰值位于500—600百帕气层,两者垂直分布特征说明,该暴雨过程凝结潜热和对流垂直输送作用均十分重要。(2)视西风动量源在600百帕以下为正值,以上为负值,说明东风动量向高层输送;视南风动量源在400百帕以下为负值,以上为正值,说明南风动量向高层输送。 

A BUDGET ANALYSIS OF LARGE SCALE HEAT, MOISTURE AND MOMENTUM IN A HEAVY RAIN PROCESS

Some recent studies of the Mei-Yu (lengthy rain) periods for the Yangtze River valley have shown that the distribution of heating sources and sinks and pricipitation nature vary from year to year and differences among individual areas of interest, weather patterns and temporal?spacial scales are great for vertical distributions of budgets. Planar fitting is used in this paper to determine the averaged temporal-spacial heat, moisture and momentum for a heavy rain process within the Mei-Yu period in the areas south of the Yangtze through June 27 to July 4,1989. Its vertical distribution is as follows: (1) The peak of the apparent heat source (Q₁) was found to be at the 400-500 hPa layer with heating rate at 16.8℃/day, while the peak of the apparent moisture sink (Q₂) was located at the 500-600 hPa layer with its order of magnitudes being 14.5℃/day. The vertical distribution of Q₁ and Q₂ indicate the importance of condensation heating and vertical transport of convection. (2) Positive apparent westerly momentum below 600 hPa accompanying negative values above it revealed an upward transport of the easterly momentum. Negative southerly momentum below 400 hPa with positive values above it showed an upward transport of southerly momentum.