华北盛夏强弱季风年的对比分析

COMPARATIVE ANALYSIS OF STRONG AND WEAK SUMMER MONSOON YEARS IN MIDSUMMER IN NORTH CHINA

本文利用45个高空台站及100余地而台站的资料,对华北地区盛夏的强季风(1973年)和弱季风年(19勺年)进行了对比分析.本文对强、弱季风年分别计算了湿静力能量、高低空流场、风的垂直结构、水汽含量及输送、水汽收支及水分循环等项目,从而得知该两年中各要素场明显差异的主要原因.

This paper,using the high altitude data from 45 stations and the surface data from 100 stations,makes a comparison between strong monsoon year(1973) and weak monsoon year(1972)in North China,and calculates wet static en- ergy,vertical structure of wind of high-and low-level flow fields,the con- tents and transport of water vapour,the income and export of water an va- pour,and water cycle,etc.in strong and weak monsoon years respectively. The following conclusions have been drawn: 1.There was a distinct occluded high energy tongue in the strong monsoon year and a low energy tongue in the weak monsoon year. 2.In the strong monsoon year,western Pacific subtropical high was strong, a wet and warm south air-flow from it met with the drier westerlies nearby 41°N and there were two water vapour transport air-flows.In the weak mon- soon year,subtropical high was weak,a wet and warm south air-flow met with westerlies nearby 35°N and there was only one water vapour transport air-flow. 3.The water vapour content of the whole layer in North China in midsum- mer was 20—40mm and water vapour content was distributed along northeast- southwest in the strong monsoon year and along latitude in the weak monsoon year. 4.There was a net income of about 95×10~8m^3/month in the strong mon- soon year and a deficiency of about 345×10~8m^3/month in the weak monsoon year. 5.Rainfall in North China in midsummer relies mainly on external water vapour supply in both strong and weak monsoon years.