Plant water use is difficult to monitor and predict in complex terrain. NASA's ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) provides new data for understanding hydrologic cycling in these forested mountain areas. Evaluation of ECOSTRESS evapotranspiration (ET) has relied primarily on eddy flux towers, but most flux towers are located in flat terrain, sampling relatively homogeneous vegetation. To address this knowledge gap, the accuracy of the ECOSTRESS land surface temperature (L2_LST) and ET (L3_ET_PT-JPL) data were evaluated against data from the U.S. Department of Agriculture (USDA) Forest Service's Coweeta Hydrologic Laboratory: a humid temperate forest ecosystem in the southern Appalachian Mountains of the southeastern U.S. with extensive data from one eddy covariance tower and five climate stations varying in elevation. ECOSTRESS LST showed a strong linear relationship with the weather station near-surface air temperature (R² = 0.85; offset = −2.5 °C), showing no difference across slope, aspect and elevation, but a higher correlation during the night than the day. ECOSTRESS tended to overestimate ET compared with our site eddy covariance measurements (R² = 0.43; RMSE = 146 W m⁻²). To evaluate potential sources of error associated with remotely-sensed inputs to the ECOSTRESS Priestly-Taylor Jet Propulsion Laboratory (PT-JPL) ET model, we ran PT-JPL using ground-based data from our site. ET estimated with locally-collected data showed much better performance in capturing variability (R² ~ 0.70), illustrating the uncertainty contributed to ECOSTRESS by the coarse scale meteorological inputs in areas of complex topography. Notably, both the ECOSTRESS LST and ET captured important topographic gradients and spatially-explicit diurnal variability. The valley floor of the Coweeta Basin was warmer than the higher elevations by 8 °C in the day, but cooler at night. On the south-facing aspects, LST and ET were higher, consistent with observations. This also highlights the ability of ECOSTRESS and PT-JPL to decouple ET from LST when and where appropriate, as they are normally inverse to one another. Our study provides the first detailed analysis of ECOSTRESS for forested ecosystems in complex terrain and offers insight for future evaluation.

在复杂的地形中，植物用水很难监测和预测。美国宇航局的空间站生态系统星载热辐射计实验 (ECOSTRESS) 为了解这些森林山区的水文循环提供了新数据。ECOSTRESS 蒸散量 (ET) 的评估主要依赖于涡流塔，但大多数通量塔位于平坦地形，采样相对均匀的植被。为了弥补这一知识差距，ECOSTRESS 地表温度 (L2_LST) 和 ET (L3_ET_PT-JPL) 数据的准确性根据美国农业部 (USDA) 林务局 Coweeta 水文实验室的数据进行了评估：一个潮湿的温带森林生态系统美国东南部的阿巴拉契亚山脉南部 来自一座涡旋协方差塔和五个海拔不同的气候站的大量数据。ECOSTRESS LST 与气象站近地表气温（R²  = 0.85；offset = -2.5 °C)，在坡度、坡向和高程上没有差异，但夜间的相关性高于白天。与我们的站点涡流协方差测量值（R ²  = 0.43；RMSE = 146 W m ^-2）相比，ECOSTRESS 倾向于高估 ET 。为了评估与 ECOSTRESS Priestly-Taylor 喷气推进实验室 (PT-JPL) ET 模型的遥感输入相关的潜在误差来源，我们使用来自我们站点的地面数据运行 PT-JPL。使用本地收集的数据估计的 ET 在捕捉变异性方面表现出更好的性能 ( R ² ~ 0.70)，说明了复杂地形区域中粗尺度气象输入对 ECOSTRESS 造成的不确定性。值得注意的是，ECOSTRESS LST 和 ET 都捕获了重要的地形梯度和空间明确的昼夜变化。Coweeta 盆地的谷底白天比高海拔地区温暖 8 °C，但夜间凉爽。在朝南的方面，LST 和 ET 较高，与观测结果一致。这也突出了 ECOSTRESS 和 PT-JPL 在适当的时间和地点将 ET 与 LST 分离的能力，因为它们通常彼此相反。我们的研究首次对复杂地形中森林生态系统的 ECOSTRESS 进行了详细分析，并为未来的评估提供了见解。