干旱区流域蒸散时空变化及遥感估算

The scientific objectives of this project is to find the suitble model for watershed scale estimation of evapotranspiration, and to analyze the temporal-spatial variation of evapotranspiration at arid regions. We focus on three aspects related to the evapotranspiration in this study: (1) Estimate the evapotranspiration at Ebinur lake watershed, at the same time, obtain the sensible heat flux and evapotranspiration at different time- and satellite pixel- scale through Aperture scintillometer, Eddy covariance systems, Bowen ratio measuring instrument and automatic weather station. The applicability of the SEBAL and SEBS models could be validated by the comparison between observed and modeled value.(2)Based on the observed water surface evaporation, analyze annual variation of land surface evapotranspiration obtained from Aperture scintillometer, Eddy covariance systems and Bowen ratio measuring instrument, discover the difference between each of the above mentioned observation method, reveal the various micrometeorological factor which have impact on land surface evapotranspiration.(3) Explore the long time series of fluctuations of evapotranspiration, analyze the monthly, seasonal and annually periodic- and nonlinear variation of evapotranspiration, in order to predict and modeling the hydrological variable, and to understanding the evapotranspiration process of the land surface at arid region.

本项目的科学目标是寻找适用于干旱区流域尺度的蒸散估算模型及分析蒸散时空变化。力图在以下3个方面进行研究。（1）利用SEBAL模型、SEBS模型估算艾比湖流域蒸散量，同时利用大孔径闪烁仪、涡动相关系统、波文比观测系统和自动气象站进行同步观测，得到不同时间尺度、不同卫星像元尺度蒸散量的显热通量和蒸散量，分析SEBAL模型、SEBS模型估算结果与仪器观测的蒸散量的差异，以验证SEBAL模型、SEBS模型在干旱区流域蒸散估算中的适用性；（2）利用蒸发皿观测的水面蒸发量，对蒸渗计法、涡动相关法、彭曼方法、波文比法观测的陆面蒸散量的年变化特征进行比较分析，研究不同蒸散观测方法的差异，揭示各种微气象要素对陆面蒸散的影响规律；（3）探讨蒸散长时间序列的波动过程，分析其月、季节、年的周期变化和非线性过程以预报、模拟水文变量，进一步理解干旱区陆面蒸散过程。

陆面蒸散过程是陆面水分平衡的重要分量，在全球水资源日益紧缺的情况下，要合理利用和分配水资源，就需要深入了解不同植被覆盖和土地利用条件下的蒸散情况。目前利用遥感技术估算干旱区流域蒸散量仍存在诸多难题。针对此问题，本项目以新疆艾比湖流域为例，应用SEBAL模型、SEBS模型估算艾比湖流域蒸散量，并利用大孔径闪烁仪、涡动相关系统、气象观测数据、蒸发皿数据验证模型的精度，并对SEBAL、SEBS模型在干旱区流域蒸散估算中的适用性进行了比较；同时探究了艾比湖流域蒸散量的时间变化特征。结果表明：近57年来艾比湖流域年潜在蒸散量以-25.05mm/10a的速度呈下降趋势，6个气象站蒸散量存在30 a 的强显著周期，各种微气象要素对陆面蒸散的影响中，气温、风速对艾比湖流域陆面蒸散的影响最大，SEBAL模型反演的日蒸散量精度（91.8%）较SEBS模型具有较高的精度（90.4%），说明SEBAL模型在干旱区流域蒸散估算中具有较高的准确性和适用性。研究结果为干旱区区域蒸散估算以及水资源合理分配方面奠定坚实的理论基础，为艾比湖流域“引喀济艾”跨流域调水后水资源评价、分配提供科学依据。