1960—2018年黄土高原地区蒸发皿蒸发时空变化特征及影响因素

Spatio temporal patterns of pan evaporation from 1960 to 2018 over the Loess Plateau:Changing properties and possible causess

蒸发是水循环的重要过程,研究黄土高原地区的蒸发皿蒸发对区域水资源利用与保护意义重大。通过收集黄土高原地区61个气象站点的蒸发皿蒸发、气温、风速、降水、相对湿度、水汽压等数据,使用Mann-Kendall检验、累积距平、线性趋势法分析了1960—2018年黄土高原地区蒸发皿蒸发的时空变化特征,运用多元回归分析法探究了影响蒸发皿蒸发的主要气象因子。研究结果表明:(1)近59 a黄土高原地区蒸发皿蒸发以-6 mm·(10a)^(-1)的速率呈下降趋势,2000年以后呈增加趋势;该区域蒸发皿蒸发存在2次转折、3个阶段的变化,1960—1974年呈增加趋势,1975—1996年呈减少趋势,1997—2018年呈增加趋势,春、夏、秋呈减少趋势,冬季呈增加趋势。(2)空间上蒸发皿蒸发整体变化和局部变化不同步,陇东、陇中黄土高原、河套地区和鄂尔多斯高原呈增加趋势,关中平原、山西黄土高原呈减少趋势。(3)平均风速、日照时数、水汽压依次是影响黄土高原地区蒸发皿蒸发的主要气象因子,平均风速减小、日照时数减少、水汽压升高是蒸发皿蒸发减少的原因;各季节中,影响春、秋季的主要气象因子为风速、夏季为相对湿度、冬季为温度。

The Loess Plateau is an important ecological conservation area,which is sensitive to climate change,located in China.It is also an important ecological governance area.Ecological restoration projects in the Loess Plateau are related to the sustainable development of the Yellow River Basin and national ecological security.Moisture is the main factor that restricts vegetation restoration in the Loess Plateau.Therefore,the variation of water resources has a direct impact on agricultural production,ecological construction,and sustainable development of the social economy in this region.In the study area water resources are relatively scarce,and evaporation is an important hydrological factor.It is necessary to study pan evaporation variations and their influence factors to provide information for ecological construction,agricultural production,and water management in the Loess Plateau.In this study,pan evaporation,temperature,wind speed,precipitation,relative humidity,and water pressure data collected from 61 weather stations were used to analyze the characteristics of pan evaporation variation and its influence factors in the Loess Plateau from 1960 to 2018,through the Mann Kendall test,cumulative anomaly,and linear trend methods.At the same time,the related driving factors were evaluated with multiple regression analysis.The results indicate that annual evaporation in the Loess Plateau showed an obvious decreasing trend at a rate of−6 mm·(10a)^(-1) in the last 59 years,but it increased after the year 2000.In the study area,two turning points and three stage changes were identified:Pan evaporation decreased between 1960 and 1974,and from 1975 to 1996,while it increased from 1997 to 2018.In addition,pan evaporation showed a decreasing trend in spring,summer,and autumn,and an increasing trend in winter.Spatially,the overall and local changes in pan evaporation were not synchronized:regions I,II,V,and VI showed an increasing trend,while the Guanzhong Plain and Shanxi Loess Plateau showed a decreasing trend.The decrease in average wind speed,sunshine hours,and the increase in water vapor pressure were important factors for the decrease in pan evaporation.The main factors responsible for this reduction were the decrease of wind speed and sunshine hours,and the increase of water vapor.In spring and autumn,the wind speed played a major role in the variation of pan evaporation,and the main influence factors in summer were precipitation,water vapor pressure,and in winter was temperature.In light of the future global warming scenarios,the variation of evaporation has become a common concern for global climate change,particularly as the decline in pan evaporation has now been reported in many regions of the world.Evaporation is an important component of the thermal balance and water budget on the Earth surface,and it is directly affected by both land use and climate change.The research on evaporation variation will help us understand the dynamics of climate change and clarify the characteristics of the water cycle in the Loess Plateau.