气候变化对黄河中上游地区潜在蒸散影响的估算

采用Penman—Monteith公式计算潜在蒸散，分析1961-2010年黄河中上游地区气候因子的变化趋势，并用偏微分方法定量分析各气候因子变化对潜在蒸散的影响。结果显示：1）近50年来黄河中上游地区气温显著升高（α〈0．01），风速和日照时间显著减少（α〈0．01）。半干旱区面积不断扩大，气候总体呈暖干变化趋势。2）潜在蒸散对实际水汽压变化最敏感，其次为最高气温、风速和日照时间，对最低气温变化最不敏感。夏季潜在蒸散对日最高气温最敏感，其他季节对实际水汽压最敏感。3）风速对年潜在蒸散变化贡献最大，其次为气温和日照时间，实际水汽压贡献最小。春夏秋冬对潜在蒸散变化贡献最大的气候因子依次为风速、日照时间、气温。温度升高、湿度减少埘潜在蒸散的正影响已被风速、辐射下降的负影响所抵消。综合考虑各气候因子对潜在蒸散的作用有助于加深对气候变化影响机制的认识，并为气候变化适应对策研究提供科学依据。

Assessing the impacts of climate change on the potential evapotranspiration in the upper-middle reach of the Yellow River

We calculated potential evapotranspiration （E0） using the Penman-Monteith equation and the analyzed temporal characteristics of climatic variables during the past 50 years （1961--2010） in the upper-middle reach of the Yellow River basin （ UMYB）. Sensitive coefficients of E0 and the contributions of climate variables to E0 in the study area were quantitatively analyzed using partial differential method. The results were as follows. 1 ） There was a significant increase in air temperature （o~ 〈 0.01 ） , and a significant decrease in wind speed and sunshine duration （a 〈0.01 ）. The climate of UMYB had become warmer and drier during the past 50 years. 2） The sensitivity coefficient of E0 to climate variables follows the order frmn high to low as actual vapor pressure （e） 〉 maximal air temperature （t） 〉 wind speed （v） 〉 sunshine hour （SH） 〉 minimal air temperature （t）. It was most sensitive to tX in summer and to e in the other seasons. 3） On the annual scale, the variation of E0 was largely contributed by v,followed by t, t, Sn and ea. The dominant factor contributing to Eo trend in spring, summer, autumn and winter was v, Stt, t and t,,, respectively. The positive effects of the increase in temperature and the decrease in humidity were offset by the negative effects of the reduction in wind speed and solar radiation. Comprehensive considerations on the impacts of all climatic variables on evapotranspiration would largely improve our knowledge on climate change and provide advices for local agricultural, forest and animal husbandry production.