根据1960—2012年海河流域45个站点平均气温、日照时数、相对湿度、风速等气象资料，选取了4个潜在蒸散发计算模型，以Penman—Monteith模型计算结果为依据，采用平均绝对误差和平均相对误差评估模型精确程度，并在此基础上研究海河流域潜在蒸散发的时空变异规律。结果表明：基于能量的模型最适用于估算海河流域的潜在蒸散发；从时间变化来看，海河流域1960—2012年潜在蒸散发总体上呈显著下降趋势，平均下降速率为2.04 mm?a-1，说明海河流域存在蒸发悖论的现象；潜在蒸散发在4个季节均呈现显著减少趋势，其中夏季减少幅度较大，冬季减少幅度最小。从空间分布来看，海河流域潜在蒸散发呈现从西北地区到东南地区阶梯式上升趋势，但大部分地区在1960—2012年时间范围发生潜在蒸散发减少现象，其中山前平原区减少趋势最为明显（<-1 mm/a），可能主要受太阳辐射减少（即全球变暗）的影响；而太行山区北部高海拔地区潜在蒸散发呈现增加的趋势，可能主要受气温升高（即全球变暖）的影响。

Based on the observation data of average temperature, sunshine hours, wind speed, and relative humidity at 45 stations in Haihe Catchment during 1960—2012, we compared three potential evapotranspiration models with the Penman—Monteith model. The absolute and relative errors were used as the model evaluation indices. Hargreaves model based on energy balance proved to be the most suitable for potential evapotranspiration estimation in Haihe Catchment. The annual potential evapotranspiration declined at a mean rate of 2.04 mm?a-1 in 1960-2012. The inter-annual variations of potential evapotranspiration in the four seasons all showed a significant decreasing trend, with the largest decline in summer and the smallest decline in winter. Spatially, the average potential evapotranspiration during 1960-2012 tended to increase from the northwest part of the region to the southeast. Moreover, the decrease of potential evapotranspiration occurred in most part of the region, especially in the southeast, which means potential evapotranspiration may be mainly impacted by global dimming. However, potential evapotranspiration in the northwest part of the region showed an increasing trend, probably due to global warming.

国家自然科学基金项目（51409109）；中央高校基本科研业务费专项资金（HUST: 2017KFYXJJ191）