人工绿洲对夏季气候变化趋势的影响

在绿洲的气候环境效应方面 ,此前的研究主要是基于个别地点的短期 (几天或几个月 )观测资料进行对比 ,分析绿洲与荒漠之间的要素差异和能量交换机制。通过细致筛选那些观测环境变化小、人口密度低、没有进行大规模水土开发地区的气象站 ,建立了反映背景变化的气候序列 ,同时选择不同地区的气象站建立了绿洲气候序列 ,分析背景与绿洲在气温、降水、水汽压、蒸发、风速等 9个气候因子近 5 0 a来气候趋势变化率的差异 ,研究绿洲发展对长年代气候变化的综合影响。结果表明 ,绿洲发展产生的气候环境效应在影响局部地区长期气候变化趋势方面是十分明显的。在夏季 ,绿洲平均气温的增温变化趋势要小于背景变化趋势 ,有些绿洲地区如吐 -善 -托盆地和叶尔羌河流域绿洲气温变化趋势还略呈下降趋势。绿洲地区对最高气温的变化趋势有着明显的抑制作用。其中 ,叶尔羌河流域绿洲和塔里木河中游地区绿洲最高气温变化趋势略呈下降趋势。绿洲地区对最低气温上升的变化趋势有一定的加强影响 ,绿洲效应使日较差正在变的越来越小。夏季绿洲对空中水汽压的增加十分明显 ,使蒸发潜力变得越来越弱 ,对降水有一定程度的增加作用。绿洲效应最为显著的一个方面是风速的变化 ,绿洲使平均风速和大风日数大幅度减少

Effects of artificial oases on climate change trend

In earlier investigations, the effects of artificial oases on climate environment were studied by analyzing the weather element differences and energy exchange mechanism between oases and deserts areas based on comparing short term (days or months) in-situ data which were collected from very few observation stations. In this paper, a background climatic series was established by selecting weather stations which are located in remote areas where (there are not so many human activities). On the other hand, we choose weather stations located on oases and built oases climatic series. The climate change ratio differences between oases and deserts in recent 50 years are explored through analyzing 9 climatic factors (air temperature, precipitation, vapor pressure, evaporation and wind speed and so on). The results show that there are distinct climatic environmental effects caused by oasis developments on local climate change. Specifically, the warm trend in oases is lower than the background change trend in summer. There were slight cool trends in some oasis sites, such as the Turpan-Shanshan-Toksun Basin and the Yarkant River watershed. Oases played an obvious restraining role in the trend of increasing maximum temperature. For example, the maximum temperatures decreases in Yarkant River watershed and the middle reaches of Tarim River. Another result is that oases strengthened slightly the increasing trends of minimum temperature. There were decreasing trends of diurnal-nocturnal temperature difference due to oasis effects. In summer, another oasis effect is that potential evaporation decreases, air vapor pressure increases then leading to more precipitation. The most significant oasis effect is the decrease of both average wind speed and the number of gale days.