高山冰川区大降水带的成因探讨

在中纬度高亚洲的高山冰川带, 由于下垫面的温度场和湿度场与周围环境的差异, 形成冷岛和高湿中心. 其结果造成水平湍流加强, 并影响内部场的湍流加剧, 使冰川区成为湿岛和局地对流加强, 形成多降水过程, 增加降水量. 当过境气流通过时, 冰川区形成阻岛, 气流活动加强, 产生降水天气. 这种作用使高山冰川带成为高降水带, 并且山地越高, 冰川面积越大, 对于气流影响越强烈. 其结果形成青藏高原外围区冰川分布广, 降水量大, 而内部降水少的格局. 大降水带的成因主要归于冷下垫面和高湿度场的作用.

High Precipitation in Glacial Region of High Mountains in High Asia:Possible Cause

Enormous resources of snow and ice are accumulated in the highlands and mountains of High Asia, and is the most concentrated glacier center in the middle and low latitudes on the Earth, covering an area of 104 850 km~2, including 23 000 km~2 in India, 16 933 km~2 in Pakistan, 5 322 km~2 in Nepal, and 49 873 km~2 in China. These glaciers receive more abundant precipitation than other regions. Annual precipitation at the equilibrium line varies from 500 to 3000 mm, and a high precipitation zone is in the glacier cover regions, formed a second maximum precipitation with altitude. High mountain massifs are advantageous for catching water vapor and the consequent development of large glaciers. Author sends a possible formation mechanism of high precipitation in glacier zone. Cold ice surface would drive an airflow sinking as the air mass passing, and result in high precipitation in glacier zone of the mountains. Other hand, there are more moisture over glacier than surrounding bar rock slopes, and a strong evaporation from glacier surface make high moisture center in the glacier cover zone. The cold surface and more moisture from glacier zone could be cause of high precipitation zone formation in glacier cover zone of High Asia.