延河流域潜在蒸散发的时空变化特征

Spatiotemporal Variation Characteristics of Potential Evapotranspiration in Yanhe River Basin

[目的]研究气候变化下潜在蒸散发(ET0)的时空特征,为区域生态需水研究和水资源管理提供科学依据。[方法]基于延河流域1978—2017年逐日气象资料,利用Penman-Monteith方法对ET_(0)进行计算,运用Mann-Kendall趋势检验法、Pettitt检验对ET 0时空变化特征进行分析,并通过Pearson相关性分析对ET_(0)变化的影响因子进行探讨。[结果]延河流域年平均ET_(0)为923.53 mm,整体呈现上升趋势。月ET_(0)呈单峰分布,高值月份出现于5—7月。季节上ET_(0)表现为:夏季>春季>秋季>冬季,夏季、春季、冬季的ET_(0)呈上升趋势,秋季呈下降趋势,春季蒸散变化速率最大。空间上,ET_(0)呈现由西部向南部增加再向东南部减少的趋势。延安站蒸散量最大,志丹站蒸散量最小,除甘泉站外其他站点的ET_(0)均呈上升趋势,甘泉附近地区存在“蒸发悖论”现象,主导因子是日照时数、2 m高风速和降水量。ET 0变化率呈现东南高西北低的分布规律,延安站变化率最大,安塞站变化最小。平均温度、日照时数、相对湿度、气压、2 m高风速、降水量等气象因子的变化趋势和变化速率时空差异显著,同一气象因子对ET_(0)的影响程度具有时空差异,相同因子不同变化趋势的组合对蒸散发的影响具有显著差异。[结论]延河流域ET_(0)变化与平均温度、日照时数、2 m高风速的变化为正相关关系,与相对湿度、气压、降雨量的变化为负相关关系,其中与日照时数相关最为密切。

[Objective]The spatiotemporal characteristics of potential evapotranspiration(ET0)under climate change were studied in order to provide scientific basis for researching regional ecological water demand and water resource management.[Methods]Based on the daily meteorological data of Yanhe River basin from 1978 to 2017,ET0 was calculated by Penman-Monteith method.The spatiotemporal variation characteristics of ET0 were analyzed by Mann-Kendall trend test and Pettitt test.And the influencing factors of ET0 change were analyzed by Pearson correlation analysis.[Results]The average annual ET0 of Yanhe River basin was 923.53 mm,showing an overall upward trend.Monthly ET0 showed unimodal distribution,and the highest value occurred from May to July.Seasonal ET0 showed as follows:summer>spring>autumn>winter.ET0 in summer,spring,and winter showed an upward trend,while it showed a downward trend in autumn.The spring evapotranspiration had the largest rate of change.Spatially,ET0 increased from the west to the south and then decreased to the southeast.The evapotranspiration at Yan’an station was the highest,and that at Zhidan station was the lowest.ET0 at other stations except Ganquan station was on the rise.There was an“evaporation paradox”phenomenon in the area around Ganquan station.The dominant factors were sunshine duration,2 m high wind speed and precipitation.The change rate of ET0 was higher in the southeast and lower in the northwest.The change rate of Yan’an station was the largest,while that of Ansai station was the least.The variation trend and rate of meteorological factors such as average temperature,sunshine duration,relative humidity,atmospheric pressure,2 m high wind speed and precipitation were significantly different in time and space.The influence of the same meteorological factor on ET0 was significantly different in time and space.The combination of different variation trends of the same factor had significant differences in the influence of ET0.[Conclusion]In general,the change of ET0 in Yanhe River basin is positively correlated with the change of average temperature,sunshine duration and 2 m high wind speed and negatively correlated with the change of relative humidity,atmospheric pressure and precipitation.The change of ET0 is the most correlated factor with sunshine duration.