蒸散发仍是全球水文循环中最大的未知项，探讨中国陆面实际蒸散发时空变化对全球气候变化、区域气候变化以及水循环模拟研究等方面具有重要价值。本项目拟利用荷兰阿姆斯特丹自由大学研发的GLEAM模型（Global Land-surface Evaporation:the Amsterdam Methodology）耦合卫星遥感数据反演的蒸散发产品ETG（时空分辨率：0.25°、日尺度）研究近32年中国陆面实际蒸散发的时空变化。本研究首先分别从点尺度(通量塔涡度相关仪观测蒸散发ET)、流域尺度（水量平衡）及与其他蒸散发产品交叉验证（Triple Collocation三配点误差模型）3个方面评价ETG产品的可靠性，然后利用滤波分析、旋转经验正交函数REOF等其他统计手段研究中国陆面蒸散发的时空变化特征。该研究对中国陆面实际蒸散发进行全面、深入的分析，为研究水循环与极端水文气象事件机制提供研究基础。

Our understanding of the changes of land evapotranspiration in recent decades remains highly uncertain so far. An improved understanding of evapotranspiration changes is of considerable importance to understand the terrestrial water cycle under climate warming. Using satellite-based evapotranspiration products ETG derived from GLEAM (Global Land Evaporation-Amsterdam Model) model, this project is to study the spatial-temporal changes of evapotranspiration in the past 32 years over China. It mainly includes two aspects: 1), ETG will be validated over the conterminous China at both point（using eddy convariance ET） and basin scales (annual basin water balance ET). We also estimate the errors of three global land-surface evaporation products(ETG, MOD16A2 an PU) using Triple Collocation methods. 2) We will analyze the spatial and temporal variability of land actual evapotranspiration over China in the past 32 years (1981-2011) using the satellite-based data ETG. .