Global daily 1-km actual evapotranspiration from 2000 to 2021 (ETMonitor-1km_2000-2021)

The evapotranspiration (ET) in this product refers to the actual land surface evapotranspiration, which is the sum of vegetation transpiration, canopy rainfall interception loss, soil evaporation, open water evaporation, and ice/snow sublimation. ET is an essential ecohydrological process that links the energy, water and carbon cycles of the land surface and plays a critical role in the Earth system. Accurate estimation of land surface ET is not only of great significance for the study of the water cycle and energy exchange processes of the Earth system, but is also valuable for applications in the effective management of water and land resources, monitoring of crop water requirements for irrigation scheduling, flood/drought monitoring and assessment for disaster management, and many others.
This data product was generated using the ETMonitor model in combination with multi-source remote sensing data and reanalysis data. The ETMonitor model established a multi-parameterization scheme to estimate the evapotranspiration components (vegetation transpiration, canopy rainfall interception loss, soil evaporation, water surface evaporation, snow and ice sublimation), taking into account the simulation of the energy balance, water balance and plant physiological processes that control the surface energy and water exchanges. All the ET components of each remote sensing pixel were first estimated, and the total actual ET of each pixel was obtained by accumulating the ET components. The validation was conducted using flux observations from the 251 ground flux sites around the world, covering a wide range of terrestrial ecosystems as well as water and snow/ice surfaces. The validation result showed that the Root Mean Square Error of daily evapotranspiration of this product generated by the ETMonitor model was 0.93mm/day. The unit of the evapotranspiration in this product is mm/day, with a conversion factor of 0.01.

本产品中的蒸散发（evapotranspiration, ET）指实际陆地表面蒸散发，即植被蒸腾、冠层降雨截留损失、土壤蒸发、开阔水体蒸发与冰雪升华的总和。ET是连接陆地表面能量、水文与碳循环的关键生态水文过程，在地球系统中发挥着至关重要的作用。准确估算陆地表面ET，不仅对研究地球系统的水循环与能量交换过程具有重要意义，还可应用于水土资源有效管理、作物需水监测以指导灌溉调度、洪涝/干旱监测评估以支撑灾害管理等诸多场景。
本数据产品依托ETMonitor模型，结合多源遥感数据与再分析数据生成。ETMonitor模型构建了多参数化方案以估算各蒸散发组分（植被蒸腾、冠层降雨截留损失、土壤蒸发、水面蒸发、冰雪升华），同时纳入控制地表能量与水分交换的能量平衡、水量平衡及植物生理过程模拟。首先逐遥感像元估算各ET组分，再通过组分累加得到单像元的总实际ET。本产品采用全球251个地面通量站的通量观测数据进行验证，覆盖了多样的陆地生态系统以及水体与冰雪下垫面。验证结果显示，ETMonitor模型生成的本产品日蒸散发的均方根误差（Root Mean Square Error）为0.93mm/天。本产品中蒸散发的单位为mm/天，转换系数为0.01。