干旱半干旱生态系统是全球最敏感、最脆弱的生态系统，水资源匮乏是旱区生态脆弱的根源和主要表现。地表蒸散作为陆地水循环的关键过程，准确评估不同时空尺度蒸散的变异信息是开展全球变化背景下旱区水资源管理和生态建设的先决条件。国内外学者已围绕不同时空尺度蒸散的评估方法开展了卓有成效的研究工作，然而地表蒸散的高精度估算仍然是陆地水循环研究的薄弱点。本项目将以中国西北部和青藏高原区域的5个生态水文观测网络为基础，通过有机结合地面-无人机遥感-卫星遥感的多元多尺度观测数据，研究土壤水热动态及其对蒸散的作用机理，开展考虑土壤水热耦合-植物生理过程的地表遥感蒸散估算研究，综合评估不同遥感蒸散算法的尺度适用性。在此基础上，开发站点-田间-流域跨尺度遥感蒸散统一估算模型和数据信息系统，为旱区生态系统的精细化管理提供服务。

Arid and semi-arid ecosystems are the most sensitive and fragile ecosystems in the world. Water scarcity is the root cause and main manifestation of ecological fragility in arid regions. Land surface evapotranspiration (ET) is a key process in the terrestrial water cycle. Accurate assessment of ET at different spatiotemporal scales is a prerequisite for the effective water resources and ecosystem management in arid areas. There is a wealth of studies on the ET observations and models at various spatiotemporal scales, while the high-resolution ET estimate is still in its infancy. Based on five eco-hydrological observation networks in the northwestern part of China and the Qinghai-Tibet Plateau, the project will investigate the mechanisms and effects of soil hydrothermal dynamics on ET estimates, through developing the ET model considering coupled soil hydrothermal-phytophysiological processes, using multi-sources of Earth Observation data (in-situ, Unmanned Aerial Systems, Satellites). Furthermore, the scale applicability of the developed ET model (and other ET models) will be investigated, in order to derive a unified EO-based ET model across scales from point to catchment. Based on the unified EO-based ET model, a web-based GIS information system will be developed as the Planning Support System to support the precision ecosystem management with cross-scale ET data.