1960 年以来新疆地区蒸发皿蒸发与实际蒸发之间的关系

利用中国新疆地区1960-2005 年109 个设有蒸发皿蒸发观测的常规气象站资料， 并结 合不同驱动场和不同陆面模式的模拟结果， 对蒸发皿蒸发及模拟的实际蒸发的年、各个季节 的变化及其它们的相互联系进行了详细的分析和讨论。结果发现， 在过去的46 年里， 年蒸发 皿蒸发总体上都表现为明显的下降趋势， 而实际蒸发在总体上显著上升， 与蒸发皿蒸发的变 化趋势相反。在80 年代中后期, 蒸发皿蒸发、实际蒸发和降水的转折点(1986 年) 一致， 进 一步说就是无论在转折点的前后， 降水增加的转折性变化与模拟的实际蒸发的转折性增加变 化一致， 而与蒸发皿蒸发减小的转折性变化相反， 这表明， 在新疆地区， 蒸发皿蒸发和实际 蒸散之间具有相反的变化关系， 这支持Brutsaert and Parlange 提出的蒸发皿蒸发和实际蒸散 之间具有互补相关关系(变化趋势相反) 的理论。分析气温、降水、湿度、云量和日照时数等 环境变量的变化趋势发现： 降水、云量等表征大气中水分特征的变量表现为明显的上升趋势， 这也间接的证明了蒸发皿蒸发和实际蒸散之间存在相反的关系， 而与各个环境变量之间相关 系数的分析则表明， 气温日较差、风速、低云量和降水是与蒸发皿蒸发和实际蒸发关系最紧 密的环境因子， 它们的变化可能是导致蒸发皿蒸发和蒸散量变化的原因。

The Relationship between Pan Evaporation and Actual Evapotranspiration in Xinjiang since 1960

Pan evaporation, an indictor of potential evaporation, has decreased during the last several decades in many parts of the world; the trend is contrary to the expectation that global warming will be accompanied by an increase in evapotranspiration, known as the pan evaporation paradox. What is the essential relation between pan evaporation and evapotranspiration? This is still an uncertain problem. In this paper, the trends of pan evaporation and evapotranspiration in Xinjiang from 1960 to 2005 are investigated using observational data and the observation-constrained simulations using of the NCAR Community Land Model (CLM). Our analysis suggests that decreasing trend of annual pan evaporation accompanies increasing trend of annual evapotranspiration, the tendency has statistical significance. We also find that there is the same turning point of 1986 for precipitation, pan evaporation and evapotranspiration, and either before the point or after the point, pan evaporation has the inverse trend with evapotranspiration and precipitation has the same trend with evapotranspiration. The above analyses indicate pan evaporation and evapotranspiration have complimentary relationship. These results support the solution of the evaporation paradox described by Brutsaert and Parlange (1998) and suggest that decreases in pan evaporation indicate an increase in terrestrial evaporation in Xinjiang. The correlation analyses show that diurnal temperature range (DTR), wind speed, low cloud cover and precipitation are most likely the driving force for the reduction of pan evaporation and the ascending evapotranspiration.q