【作者】 张静；

【导师】 宋小燕；

【作者基本信息】 西北农林科技大学 ， 工程硕士（专业学位）， 2019， 硕士

【摘要】 气候变化和人类活动改变了全球的水文循环过程,导致水资源在时间和空间上重新分配,进而影响生态环境的良性循环和人类社会的经济发展。蒸散发在联络大气过程和陆面过程的水文循环中起关键作用。由于蒸散发最直接受到复杂下垫面条件和气候变化综合影响,难以精确估算,因此实际蒸散发（ET_a）的研究是一个热点更是一个难点。Budyko理论框架具有坚实的理论基础和明确的物理含义,是水文学研究的前沿和热点之一。论文以位于中高纬度地区的松花江流域为研究区,以Budyko水热耦合平衡假设为主要理论基础。首先分析了1959-2014年松花江流域水热条件的时空变化;然后基于Budyko假设模拟了松花江流域长序列ET_a;最后重点基于傅抱璞框架综合土壤水蓄变量因子（（35）S）,改进了年尺度和月尺度的水热耦合方程。得出的主要结论如下:（1）松花江流域水热条件时空演化:分析了降水（P）和径流（R）的时空变化及两者的空间趋势一致性;探讨了研究区ET₀和各气象要素的空间变化特征及其空间分布一致性;采用敏感系数和贡献量方法剖析了影响ET₀（生长季5-9月）主导因素的时空分异特征;分析了年际尺度水量收支状况。结果表明:ET₀从西南向东北递减的主导因子是逐渐下降的日照时数、逐渐增加的相对湿度以及逐渐减少的平均气温。P、ET₀、R均呈现下降趋势,说明该区的水文循环进程在减弱。（2）基于Budyko假设对松花江流域长序列ET_a的模拟:探讨了傅抱璞方程在研究区的适用性,下垫面参数（w）的年际变异特征;估算和分析了ET_a的时空变化;辨析了研究区径流变化的归因;探讨了不同ET₀的计算公式对傅抱璞框架应用的影响。结果表明:傅抱璞方程估计的ET_a具有较高精度,年际尺度上植被覆盖度的变化影响w值。ET_a以-0.8mm/10a的速率减少,且呈现出降-升-降-升的阶段特征和“东多西少”的空间分布格局。下垫面变化对径流减少的贡献率为73%,Penman-Monteith（P-M）与Hargreaves（Har）法在模拟效果和敏感性分析结果方面相差不大。（3）傅抱璞公式的改进:综合土壤水蓄变量因子（（35）S）,改进了年尺度和月尺度的水热耦合方程,分析了不同时间尺度ET_a的时空变化特征及其驱动机制;初探了MOD16遥感ET_a对不同Budyko框架在松花江流域适用性的影响。结果表明:模型中增加（35）S后,年尺度和月尺度（哈尔滨汇水区）模型精度均有所提高。干燥度（ET₀/P）越大的区域,方程适用性越好。年尺度上P对ET_a的贡献量空间分布与ET₀、P、（35）S对ET_a总贡献量空间变化一致,表明该流域属于水分控制区,（35）S对ET_a有影响,但是影响不显著。月尺度上除7月ET₀对ET_a的敏感系数最大外,其他月份ET_a对各因子的敏感性表现为P>ET₀>（35）S。年尺度上以水量平衡法计算的ET_a作为实测值的模型精度高于以MOD16遥感数据作为实测值的模型精度;傅抱璞公式和M-Choudhury-Yang公式的模拟效果相差不大。研究结果将给中高纬度地区构建不同时间尺度的水热耦合方程提供理论基础,对研究气候变化对水文过程的影响具有非常重要的意义,另外在水资源规划利用、干旱监测方面等具有指导意义。更多还原

【Abstract】 Climate change and human activities have changed the process of global hydrological cycle,leading to the redistribution of water resources in time and space,and then affecting the benign cycle of the ecological environment and the economic development of human society.Evapotranspiration plays a key role in the hydrological cycle that links atmospheric processes with land surface processes.Because evapotranspiration is most directly affected by complex underlying surface conditions and climate change,it is difficult to estimate accurately,so the study of actual evapotranspiration（ET_a）is a hot topic and a difficult point.In this paper,the Songhua River basin located in the middle and high latitudes is taken as the research area,and the Budyko Hydrothermal Coupling equilibrium hypothesis is taken as the main theoretical basis.Firstly,the temporal and spatial variations of hydrothermal conditions in Songhua River basin from 1959 to 2014 are analyzed;secondly,the long-range ET_a in Songhua River basin is simulated based on Budyko hypothesis;finally,the coupling equation of water and heat at the annual and monthly scales is improved by synthesizing the variable factors of soil water storage based on Fu Baopu framework.The main conclusions are as follows:（1）Spatial and temporal evolution of hydrothermal conditions in Songhua River Basin:Spatial and temporal variations of precipitation（P）and runoff（R）and their spatial trend consistency were analyzed;the spatial variation characteristics of ET₀ and meteorological elements and their spatial distribution consistency were discussed;and the dominant factors affecting ET₀（growth season,May-September）were analyzed by sensitivity coefficient and contribution method.The status of spatial and temporal differentiation were analyzed,and the characteristics of annual water budget were analyzed.The results show that the main factors of ET₀ decreasing from southwest to northeast are the decreasing sunshine hours,the increasing relative humidity and the decreasing average temperature.P,ET₀ and R all showed a downward trend,indicating that the hydrological cycle process in the area was weakening.（2）Based on Budyko hypothesis,the simulation of long-sequence ETa in Songhua River basin is carried out:the applicability of Fu Baopu equation in the study area and the interannual variation characteristics of underlying surface parameters（w）are discussed;the temporal and spatial variation of ET_a is estimated and analyzed;the attribution of runoff variation in the study area is identified;and the influence of different ET₀ calculation formulas on the application of Fu Baopu framework is discussed.The results show that the ET_a estimated by Fu Baopu equation has high accuracy,and the change of vegetation coverage affects the w value on the interannual scale.ET_a decreases at a rate of-0.8mm/10a,and presents the stage characteristics of"down-up-down-up"and the spatial distribution pattern of"more East and less west".The contribution rate of underlying surface change to runoff reduction is 73%.There is little difference between Penman-Monteith（P-M）and Hargreaves（Har）methods in simulation results and sensitivity analysis results.（3）Improvement of Fu Baopu’s formula:Combining the variable factors of soil water storage（（35）S）,the coupling equation of water and heat at annual and monthly scales was improved,and the temporal and spatial variation characteristics and driving mechanism of ET_a at different time scales were analyzed.The effects of MOD16 remote sensing ET_a on the applicability of different Budyko frameworks in Songhua River Basin were preliminarily explored.The results show that the accuracy of annual scale and monthly scale（Harbin catchment area）models is improved after adding（35）S to the model.The greater the dryness（ET₀/P）,the better the applicability of the equation.The spatial distribution of P contribution to ET_a is consistent with that of ET₀,P and（35）S contribution to ET_a on an annual scale,indicating that the basin belongs to a water control area,and（35）S has an impact on ETa,but the impact is not significant.On the monthly scale,the sensitivity of ET_a to ET_a was P>ET₀>（35）S in other months except July.On the annual scale,the model accuracy of ET_a calculated by water balance method is higher than that of MOD16 remote sensing data.The simulation results of Fu Baopu formula and M-Choudhury-Yang formula are similar.The results of this study provide a theoretical basis for the construction of water-heat coupling equations at different time scales in mid-high latitudes,and are of great significance for the study of the impact of climate change on hydrological processes,as well as for the planning and utilization of water resources and drought monitoring.更多还原