摘要:利用中国西北中部具有代表性的非季风区、夏季风影响过渡区和季风区的7个高空站的2013年夏季晴天07时、13时、19时（北京时）的大气边界层资料，通过分析大气边界层位温、比湿、风速的垂直结构，发现大气边界层结构及厚度在不同区域的分布特征：稳定边界层厚度、残余层顶高度和对流边界层厚度从非季风区、夏季风影响过渡区至季风区出现阶梯性大幅降低，从非季风区至夏季风影响过渡区，以及从夏季风影响过渡区至季风区，对流边界层厚度降幅依次为25.6%和81.8%，稳定边界层厚度降幅依次为58.3%和41.8%；在稳定边界层条件下，可观察到低空急流的存在，非季风区低空急流出现高度明显高于夏季风影响过渡区和季风区，且非季风区的低空急流风速也明显大于夏季风影响过渡区和季风区。通过分析与大气边界层发展最为密切的陆面热力因素在不同气候区的分布，净辐射值、日地-气温差最大值以及感热通量值在非季风区大于夏季风影响过渡区和季风区，从陆面热力过程为非季风区大气边界层厚度大于夏季风影响过渡区和季风区提供了理论依据。
关键词:夏季风影响过渡区/
大气边界层结构特征/
大气边界层厚度/
陆面热力因素
Abstract:Sounding data observed at 0700 BJT (Beijing time), 1300 BJT and 1900 BJT at seven sounding stations in central Northwest China on clear days in the summer of 2013 are used in the present study. The seven sounding stations are distributed in the non-monsoon zone, the summer monsoon transition zone and the monsoon zone, respectively. Vertical structures of potential temperature, specific humidity, wind speed, and atmosphere boundary layer thickness over different zones are analyzed. The results show that there are differences in the structure characteristics and thickness of the atmosphere boundary layer in different zones. The stable boundary layer thickness, the residual layer height and the convective boundary layer thickness decrease significantly from the non-monsoon zone to the summer monsoon transition zone and from the summer monsoon transition zone to the monsoon zone. The convective boundary layer thickness decreases by 25.6% from the non-monsoon zone to the summer monsoon transition zone, and the decrease is 81.8% from the summer monsoon transition zone to the monsoon zone. The stable boundary layer thickness decreases by 58.3% from the non-monsoon zone to the summer monsoon transition zone, and the decrease is 41.8% from the summer monsoon transition zone to the monsoon zone. Low-level jets can be observed in stable boundary layer, and the height of the low-level jet in the non-monsoon zone is higher than that in the summer monsoon transition zone and the monsoon zone. A similar phenomenon is found for the wind speed of the low-level jet. Based on analysis of the distribution of land surface thermal factors in different climatic regions, it is found that the distributions of the net radiation, the daily maximum difference between surface temperature and surface air-temperature (Ts-Ta) and the sensible heat fluxes are similar to the distribution of the convective boundary layer thickness. These land surface thermal factors in non-monsoon zone are larger than those in the summer monsoon transition zone and the monsoon zone. Results of the present paper provide a theoretical basis for the study of differences in the structure and thickness of the atmospheric boundary layer in different zones.
Key words:Summer monsoon transition zone/
Structural characteristics of atmospheric boundary layer/
Atmospheric boundary layer thickness/
Land surface thermal factors
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