摘要:基于永定河流域1958～2018年14个气象站的逐日观测数据，采用气候倾向率、Mann–Kendall趋势检验法分析蒸发皿蒸发量时空变化特征，并通过完全相关系数和多元回归分析识别气候因子与蒸发量的相关程度并定量计算其贡献率。结果表明：在全球气候变暖的背景下，60年来永定河流域气温以0.29°C/10 a的速率上升，而蒸发皿蒸发量不增反减，以－48.88 mm/10 a的速率显著下降（标准化统计量Z=－4.5），该流域存在明显的“蒸发悖论”现象。流域蒸发量表现出显著的时空分布差异性，在季节上，春、夏季蒸发量分别占全年蒸发量的35%和37%，且春、夏两季蒸发量下降趋势较为显著；在空间上，永定河流域下游平原区下降趋势较上游山区（天镇、蔚县等地区）更为显著。完全相关分析表明，净辐射、平均风速和空气饱和差与蒸发量具有较强的相关性；贡献率分析表明，与基准期 1958～1979 年相比，1980～2018 年平均风速和净辐射减少对蒸发量减少的贡献率分别为77%和66%，空气饱和差的贡献率为－41%，净辐射和平均风速的减少是导致蒸发皿蒸发量下降的主要影响因素。
关键词:蒸发皿蒸发量/
蒸发悖论/
影响因子/
贡献率
Abstract:Based on the daily observation data of 14 meteorological stations in the Yongding River basin from 1958 to 2018, the variation characteristics of pan evaporation over 60 years were analyzed using climate tendency rate and Mann–Kendall trend test. Moreover, the main influencing factors were identified by complete correlation coefficient and multivariate regression analysis. Results showed that under the background of global warming, the temperature of the Yongding River basin increased at the rate of 0.29°C/10 a in 60 years, while pan evaporation decreased significantly at the rate of ?48.88 mm/10a (standardized statistics Z = ?4.5). Evidently, an “evaporation paradox” phenomenon exists. There are significant differences in the spatial and temporal distribution of evaporation in the basin. Evaporation decreases significantly in spring and summer, accounting for 35% and 37% of the annual evaporation, respectively. The evaporation is unevenly distributed over an area, and the downtrend of the downstream of the Yongding River basin is more significant than that in the upper regions of the mountain area (Tianzhen, Yuxian, and other areas). Net radiation, average wind speed, and air saturation difference have a strong correlation with the decrease in evaporation. Compared with the base period of 1958–1979, the decrease in the average wind speed and net radiation during 1980–2018 contributed to 77% and 66% decrease in evaporation, respectively, and the contribution rate of the air saturation difference is ?41%. The decrease in net radiation and average wind speed is the main factor leading to the decrease of evaporation. The air pollution problem and change in the underlying surface of the Yongding River basin cause the net radiation and average wind speed to decrease significantly, which may lead to serious water imbalance in the lower plains of the basin.
Key words:Pan evaporation/
Evaporation paradox/
Influencing factors/
Contribution rate
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