State Key Laboratory of Remote Sensing Science, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China.
College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China.
Sci Total Environ. 2019 Dec 10;695:133787. doi: 10.1016/j.scitotenv.2019.133787. Epub 2019 Aug 6.
Satellite-derived terrestrial latent heat flux (LE) models are useful tools to understand regional surface energy and water cycle processes for terrestrial ecosystems in the Heihe River basin (HRB) of Northwest China. This study developed a satellite-derived hybrid LE model parameterized by three soil moisture (SM) constraints: SM, relative humidity (RH), and diurnal air temperature range (DT); and assessed model performance and sensitivity. We used MODerate Resolution Imaging Spectroradiometer (MODIS) and eddy covariance (EC) data from 12 EC flux tower sites across the HRB. The hybrid model was trained using observed LE over 2012/2013-2014, and validated using observed LE for 2015 and leave-one-out cross-validation. The results show that the three SM constraints schemes exhibited some modeling differences at the flux tower site scale. LE estimation using SM achieved the highest correlation (R = 0.87, p < 0.01) and lowest root mean square error (RMSE = 20.1 W/m) compared to schemes using RH or DT schemes. We then produced regional daily LE maps at 1 km × 1 km across the HRB for 2013-2015. Regional analysis shows that our LE estimates from all three constraint models exhibited large spatial variability and strong seasonal and annual variations, attributed to differences in parameterizing the model water constraints. This study provides data and model based evidence to improve satellite-derived hybrid LE models with regard to water constraints.
卫星衍生陆面潜热通量（LE）模型是理解中国西北黑河流域（HRB）陆地生态系统区域表面能量和水循环过程的有用工具。本研究开发了一种基于三种土壤湿度（SM）约束参数化的卫星衍生混合 LE 模型：SM、相对湿度（RH）和日气温范围（DT）；并评估了模型性能和敏感性。我们使用 MODerate Resolution Imaging Spectroradiometer（MODIS）和涡度协方差（EC）数据，来自 HRB 内的 12 个 EC 通量塔站点。混合模型使用 2012/2013-2014 年观测到的 LE 进行训练，并使用 2015 年观测到的 LE 进行验证和留一交叉验证。结果表明，三种 SM 约束方案在通量塔站点尺度上表现出一些建模差异。与使用 RH 或 DT 方案相比，使用 SM 进行 LE 估算具有最高的相关性（R=0.87，p<0.01）和最低的均方根误差（RMSE=20.1 W/m）。然后，我们在 2013-2015 年期间生成了整个 HRB 地区的 1km×1km 逐日 LE 地图。区域分析表明，我们从所有三种约束模型得出的 LE 估计值表现出很大的空间变异性和强烈的季节性和年度变化，这归因于模型水约束参数化的差异。本研究为改进基于水约束的卫星衍生混合 LE 模型提供了数据和模型依据。
