“蒸发悖论”在黄河流域的探讨

Evaporation Paradox in the Yellow River Basin

利用黄河流域72个气象站点1960-2010年的气象资料,系统分析了过去51年间气温、降水量以及潜在蒸散量的变化趋势,研究了气温、降水量与潜在蒸散量之间的长期变化趋势关系,对影响潜在蒸散量下降的主要因子进行了探讨,重点对黄河流域是否存在"蒸发悖论"进行验证。研究结果表明:(1)过去51年间,黄河流域内气温增加显著、潜在蒸散量呈下降趋势,总体上存在"蒸发悖论";(2)"蒸发悖论"具有空间上和时间上的不一致性,随着气温增加,春、夏、冬三季潜在蒸散量呈减少趋势,减少区域主要集中于山西、河南大部分区域以及甘肃、宁夏、内蒙古、陕西等少部分区域;时间上主要表现在1960-1979年潜在蒸散量变化趋势不明显,1980-2010年气温与潜在蒸散量变化趋势在空间分布上的逆向关系更加明显;(3)过去51年间,降水量无论是年际还是夏、秋季变化趋势都不明显,降水量与潜在蒸散量时空变化分布上大体呈现逆向变化关系;(4)从气象要素变化对潜在蒸散量变化的贡献率来看,近51年来风速的明显减小是导致黄河流域潜在蒸散量减少的主导因素。

Based on the data of 72 meteorological stations in the Yellow River Basin from 1960 to 2010, this paper analyzed the changing trends in potential evapotranspiration and air temperature, and the main factors affecting the decrease of potential evapotranspiration. It also discussed the existence of the ＂evaporation paradox＂ （the contract between expectation and observation of evaporation）. The results are indicated in the following aspects. （1） In the past 51 years, the air temperature increased significantly and the potential evapotranspiration decreased, therefore the evaporation paradox actually existed in the Yellow River Basin. （2） The ＂evaporation paradox＂ is not consistent spatially or temporally： as the temperature increased, potential evapotranspiration decreased in spring, summer and winter over most parts of Shanxi and Henan, and some parts of Gansu, Ningxia, Inner Mongolia, and Shaanxi. In the past 51 years, the changing trend of potential evapotranspiration is not significant from 1960 to 1979, and the changing trends of temperature and the potential evapotranspiration were negatively correlated at most of the stations. （3） In the past 51 years, the changing trends of annual, summer and autumn precipitation are not obvious, and the precipitation and potential evapotranspiration exhibit a contrary trend. （4） In terms of the contribution rate of meteorological elements change to potential evapotranspiration change, a significant decrease of wind speeds in the 51 years is the dominating factor leading to the decrease of potential evapotranspiration in the Yellow River Basin.