利用彭曼公式计算了80年代以来黄河上游流域蒸散量,分析了该地区蒸散量、日照时数、气温、空气饱和差等气候因子的变化趋势,着重研究了诸因子对蒸散量的影响。研究发现,黄河上游流域蒸散量呈逐年增大趋势,并以每年3.25 mm的速度递增;而作为主要影响因子的日照时数则以每年3.6小时的速度增加;气温同样表现出逐年升高的趋势,其气候倾向率为0.4℃/10 a;空气饱和差也以每年0.02 hPa的速度递增。因此,可以认为,黄河上游流域日照时数、气温及饱和差的增加,加剧了草地蒸散量的增大,而蒸散量的增大和降水量的减少则直接影响到了黄河上游流量的减少和草地荒漠化的蔓延。

By using of Penman formula, the authors calculated the evapotranspiration since 1980s, and analyzed the variation tendency of some climatic factors such as evapotranspiration, sunshine duration, air temperature, air saturation deficitetc, and focused on their impact to the evapotranspiration. The results show that the evapotranspiration is increasing annually with the speed of 3.25 mm over Yellow River upper stream area;while the sunshine duration which is considered as main impact factor, is increasing with the speed of 3.6 h/a;air temperature is appearing the increasing tendency, and its climatic tendency is 0.4℃/10 a; air saturation deficit is increasing with 0.02 hPa/a. Therefore, we could think that the evapotranspiration is greatly increasing as increment of sunshine duration and air temperature deficit over Yellow River upper stream area. But the increment of evapotranspiration and decrement of precipitation amount impact directly on the decrement of flow curve and expanding of grassland' s desertization over Yellow River upper stream.