【作者】 王硕；

【导师】 崔晨风；

【作者基本信息】 西北农林科技大学 ， 水利工程， 2025， 硕士

【摘要】 陆表蒸散发（ET）是全球水循环中的关键变量,显著受到气候变化和植被绿化的影响。细化了解ET及其组成成分如何响应不断变化的气候条件以及植被状况,对于提高对陆地水循环过程的认识以及水资源可用性的精细化评估等一系列问题的科学理解至关重要。本研究首先基于PML＿V2陆地蒸散发数据集处理得到全球旱区ET及其三个组分植被冠层蒸腾（Ec）、土壤蒸发（Es）和植被截留蒸发（Ei）,接着以温度、降水及地表净太阳辐射（SNSR）表征气候变化,以叶面积指数（LAI）表征植被变化,在季和年时间尺度,利用Sen趋势分析法、Hurst指数法对全球旱区陆表蒸散发及其影响因素的时空变化特征进行了深入分析,利用逐像元偏相关分析及基于岭回归模型的贡献率分析方法对全球旱区陆表蒸散发趋势变化过程中的内外驱动力进行了量化。此外,基于各组分占比,对全球旱区陆表蒸散发的内部结构变化特征及归因进行了量化,主要研究结果如下:（1）2003-2018年全球旱区ET多年均值为375.4mm,空间异质性显著。Ec、Es和Ei多年平均值分别为173.7 mm、185.1 mm和16.6mm,分别占ET的46.3%、49.3%和4.4%。Es是全球旱区ET的主要组成部分。季尺度上,Es在春季、秋季和冬季为均为ET的最大组成部分,在春季尤其明显,占总ET的56.7%。Ec是夏季ET的最大组成部分,占总量的50.3%。全球旱区ET变化趋势在未来呈现持续增长、由下降转变为上升、持续下降、由上升转变为下降态势的地区分别占比29.6%、20.1%、19.6%、30.7%。全球旱区Ec、Ei变化趋势在未来保持持续增长态势的地区占比分别为37.8%和33.9%,全球旱区Es则在约24%的地区呈现持续下降态势。各影响因素中,全球旱区温度以每年0.032℃、LAI以每年3.07×10^-4的速度呈现增长趋势,且具有明显的季节特征。全球旱区降水及辐射则分别以每年0.03mm、0.24MJ/m²的速度呈现下降趋势。（2）植被是主导全球旱区ET变化区域最大的影响因素,在全球43%的旱区地区对ET变化起主导作用,并且同时也是主导Ec、Es和Ei变化区域最大的影响因素,分别在全球旱区82%、34%和67%的地区发挥主导作用。在全球干旱区,植被同时是驱动ET及其组分时空变化最大的贡献因子,并且这一驱动模式在季尺度上保持成立。对于气候因素,它们导致ET变化的相对影响能力相近,但在发挥实际影响力时,温度对ET变化的贡献要明显高于其他气候因素。ET的组成成分中,Es在ET时空演变过程中发挥了显著主导作用,其对ET变化的绝对贡献（60.3%）约为具有近似体量的Ec的两倍。此外,通过对比分析,发现ET主要通过Es响应气候变化,而其对植被变化的响应主要由Ec和Ei驱动,但该响应强度被Es显著抑制。（3）研究期间全球旱区Ec占比和Ei占比分别以1.65×10^-3/年、1.2×10^-5/年的速度呈上升趋势。Es占比则以1.7×10^-3/年的速度呈下降趋势,呈现明显下降趋势的地区主要分布在北美州旱区中部、非洲旱区南端、亚洲旱区东南部等地区。季尺度上,Ec占比和Ei占比上升趋势最显著的季节分别是冬季和秋季,Es占比在冬季下降趋势最大。植被是主导全球旱区Ec占比、Es占比、Ei占比三者变化范围最大的主导因素,分别在全球旱区55.7%、60.9%、56%的地区对Ec占比、Es占比、Ei占比变化占据主导地位。同时,植被也是年及季尺度对全球旱区Ec占比、Es占比以及Ei占比变化最大的贡献因子,且其对三个组分占比变化的相对贡献率及绝对贡献率均要显著高于其余气候影响因素,贡献率始终保持较高水平。更多还原

【Abstract】 Terrestrial evapotranspiration（ET）is a key variable in the global water cycle,notably affected by climate change and vegetation greening.A refined understanding of how ET and its components respond to changing climatic and vegetation conditions is crucial for enhancing scientific knowledge on issues such as terrestrial water cycle processes and the more precise assessment of water availability.In this study,we firstly processed the PML＿V2 terrestrial evapotranspiration dataset to obtain the global dryland ET and its three components of plant canopy transpiration（Ec）,soil evaporation（Es）,and evaporation of precipitation intercepted by vegetation（Ei）,and then characterised the climate change in terms of temperature,precipitation,and surface net solar radiation（SNSR）,and the vegetation change in terms of the leaf area index（LAI）.At the seasonal and annual time scales,we used methods such as Sen’s slope trend analysis and the Hurst index to analyze the spatiotemporal variation characteristics of global dryland ET and its influencing factors.Additionally,pixel-level partial correlation analysis and contribution rate analysis based on the ridge regression model were used to quantify the internal and external drivers of ET trend changes across global drylands.Moreover,based on the proportions of each component,the internal structural changes and attributions of global dryland ET were quantified.The main results of the study are as follows:（1）The multi-year average of ET in the global drylands from 2003 to 2018 was 375.4mm,with significant spatial heterogeneity.The multi-year averages of Ec,Es,and Ei were173.7 mm,185.1 mm,and 16.6 mm,which accounted for 46.3%,49.3%,and 4.4%of ET,respectively.Es was the major component of ET in the global dry zone.On the seasonal scale,Ec was the largest component of ET in summer,accounting for 50.3%of the total.Es was the largest component in spring,autumn and winter,and was especially pronounced in spring,accounting for 56.7%of the total ET.In the future,the trend of ET in the global dryland areas showed a continuous increase,a change from a decreasing to an increasing trend,a continuous decrease,and a change from an increasing to a decreasing trend,accounting for29.6%,20.1%,19.6%,and 30.7%of the total ET,respectively.The proportion of regions with sustained growth in global dryland Ec and Ei trends in the future is 37.8%and 33.9%,respectively,while global dryland Es shows a sustained decline in about 24%of the regions.Among the influencing factors,the global dryland temperature showed an increasing trend at a rate of 0.032°C per year and LAI at a rate of 3.07×10^-4per year,with obvious seasonal characteristics.Precipitation and radiation in the global dry zone showed a decreasing trend at 0.03 mm and 0.24 MJ/m²per year,respectively.（2）Vegetation is the largest influence on ET changes in the global drylands,dominating ET changes in 43%of the drylands,and is also the largest influence on Ec,Es,and Ei changes in 82%,34%,and 67%of the drylands,respectively.Vegetation is simultaneously the largest contributor to driving spatial and temporal changes in ET and its components in the global dry zone,and this driving pattern holds at seasonal scales.For climatic factors,they have similar relative influencing capacity to cause ET changes,but when exerting actual influence,temperature contributes significantly more to ET changes than other climatic factors.Among the components of ET,Es plays a significantly dominant role in the spatio-temporal evolution of ET,and its absolute contribution to ET changes（60.3%）is about twice as much as that of Ec,which has an approximate volume.In addition,comparative analyses revealed that ET responded to climate change mainly through Es,while its response to vegetation change was mainly driven by Ec and Ei,but the strength of this response was significantly suppressed by Es.（3）During the study period,the proportions of Ec and Ei in the global drylands showed an increasing trend at 1.65×10^-3/year and 1.2×10^-5/year,respectively,while the proportion of Es showed a decreasing trend at 1.7×10^-3/year,with the regions showing significant decreases mainly across central North American arid zones,the southern tip of arid regions in Africa,and the southeastern parts of Asian arid areas.On the seasonal scale,the seasons with the most significant upward trends in the proportions of Ec and Ei were winter and autumn,respectively,and the the proportion of Es had the largest downward trend in winter.Vegetation was the dominant factor that dominated the largest range of changes in the proportions of Ec,Es,and Ei in the global drylands,dominating the changes in the proportions of Ec,Es,and Ei in 55.7%,60.9%,and 56%of the global drylands,respectively.Meanwhile,vegetation is also the largest contributor to the changes of the proportions of Ec,Es and Ei in the global drylands at annual and seasonal scales,and its relative and absolute contributions to the changes of the three proportions of the three components are significantly higher than those of the other climate influences,and the contribution rates are always at a high level.更多还原