西天山山区气候变化与灌区绿洲气候效应

对近40a西天山山区气候变化的特点及其变化趋势进行了分析,并以阿克苏源流区、阿克苏灌区以及叶尔羌河灌区的14个气象站的观测资料(1961—2000年)为基础,重点研究了灌区的气候变化及绿洲气候效应.20世纪90年代以来,各区域的气温增高,降水增多,其中在源流地区降水增加幅度最大,而沙尘暴、浮尘和大风日数都有明显的下降.最后,讨论了气候变化与绿洲发展的关系.

Climate Change in the Western Tianshan Mountainous and Climate Effect of Oasis

In the West Tianshan Mountainous the environment around weather stations less changes because of far from city and little influence of human activities. So there climate change has more persuasion. It is proved that climate warming is a common phenomenon in Xinjiang Region, reflecting the global change. Analysis indicate that there is an obvious warming-wetting tend in the West Tianshan Mountainous, the upper reaches and the irrigation land of the Aksu River, and the irrigation land of the Yarkant River. Compared with the multi-year average, in the 1990s, the mean annual air temperature in the West Tianshan Mountainous increased for 0.5 ℃, and the warming occurred mostly in autumn and secondly in winter. Glacier and snow resources in the Tianshan Mountainous would be influenced by the climate warming, the mean annual precipitation in the West Tianshan Mountainous increased for 6.7%, and the increasing occurred mostly in winter and secondly in summer. In the Tianshan Mountainous, precipitation is the main supply of surface water, and also the precipitation increasing is an importance reason for the steady of surface runoff in the headwaters of the Aksu River in the last 40 years. In the upper reaches and the cultivated land of the Aksu River and the cultivate land of the Yarkant River, mean annual air temperature increased for 0.2～0.4 ℃, and annual precipitation increased for 22.1%～34.2%. Precipitation increasing in the headwaters is more than that in the plain irrigation area, that is, precipitation increased more and more near the Tianshan Mountainous, which is the area with the most precipitation increasing in Xinjiang Region. It is found that the sum days of floating dust, sand-dust storm and strong wind have obviously downtrend. The 1990s was the least period of the sum days of floating dust, sand-dust storm and strong wind. Decreasing of the sum days is maybe related to development of manual oasis ecosystem, geography position of oasis and increasing of vapor content in air. On the other hand, global warming should result in intensive water cycle, changing distribution of precipitation, and bringing on precipitation increasing in some areas. Expanding plantation in the mountain foot in the Aksu River basin, the precipitation increasing is accelerated by moisture evaporation of the farmland in the mountain foot. However, expanding plantation in the lower reaches of the Tarim River, which is far away from mountain, does not gain the effect of moisture evaporation of the farmland to form local precipitation. Quite the reverse, this expanding plantation would beget precipitation decreasing and speed desertification. Therefore, the respond of climate is all dissimilarity to the same human activities in the mountain foot of the Aksu River basin and the lower reaches of the Tarim River.