亚洲中部干旱气候研究综述与机理分析

综述了亚洲中部干旱气候若干研究进展,并对亚洲中纬度干旱区形成机理进行了深入分析。依据大尺度气候分类法将全球陆地划分为季风、地中海及西风带气候区,分别对应于年内季节循环中多雨—高温的同位相、反位相及不相关等类型水—热配置特征。亚洲中部干旱区南北部分属地中海和西风带气候区,其不同水—热位相配置又对应于不同的水汽通量及其散度等特征。研究揭示了欧亚大陆中部干旱区形成于降水不足且季节性水—热配置不当,起因于大气环流平均槽脊季节变化引起的大气动力—热力配置,其根源是海陆热力差异及大地形对大气环流强迫的结果。本文还讨论了季风区与非季风区之间平均气流水汽散度的季节性互动,以及行星尺度上不同气候区之间平均气流与瞬变涡动水汽散度之间的配置等问题。

A summary of aridity studies for central Asia with mechanism analysis

This paper aims at exploring the mechanism of arid climate along the Silk Road in the centre of Eurasian continent basing on related researches, especially the publication for large-scale climate classification. There are approximately three types of climate in the world, i.e., monsoon, Mediterranean and westerly climates, corresponding the pair of seasonal precipitation and air temperature that kept in phase, anti-phase and out of phase, respectively. Four regional climate around Tibetan Plateau are identified as Mediterranean climate in Central Asia, Westerly climate in the north part of Central Asia throughout Northwest China, and monsoon climate in East Asia and South Asia, with different water-thermal matches and moisture transport with divergence. The most important finding is that the more/less seasonal precipitation rate corresponds large-scale moisture transport northward/southward coupled with moisture convergence/divergence. The mechanism of the arid climate pattern in central Eurasia is not only insufficient precipitation, but also the mismatch between the temperature and precipitation during seasonal cycle, which results from the mismatch in dynamics and thermal dynamics due to seasonal changes of the stationary waves in mid-latitude circulation of atmosphere, which is forced by the thermal difference between land-sea thermal contrast and, especially, the large mountains. Finally, a discussion is devoted to mutually engagement between seasonal changes in the moisture flow and divergences over the monsoon zone and non-monsoon zones in Eurasian continent in addition to the coupling between large-scale moisture and transient eddy divergences.