考虑含水量的土壤热红外方向发射率波谱模型构建与应用研究

Land surface temperature (LST) is one of the most important parameters in the physical processes of surface energy and water balance at local through global scales, and land surface emissivity (LSE) is a key parameter in LST retrieval. Most existing LST retrieval algorithms ignored the directionality of soil emissivity, which impeded the improvement of LST retrieval accuracy. In this project, the soil was chosen as study object. Based on ASTER spectral library and emissivity measurements under different controlled conditions, the spectral features of soil thermal infrared emissivity spectrum and the relationships between soil emissivity and soil parameters which are sensitive to the soil emissivity will be analyzed. The soil moisture content and view angle are chosen for modeling, based on field emissivity measurements and radiation transfer theory, we intend to build a moisture content dependent thermal infrared directional emissivity spectral model for soil. Then, the model will be validated using ground emissivity measurements, and further extended to remote sensing pixel-scale through analysis with remote sensing emissivity product. At last, the proposed soil directional emissivity model will be used in current LST retrieval algorithm, and long term ground LST measurements will be used for validation. This project may providing some essential theoretical and technological solutions to parameterize key factors which sensitive to soil emissivity and directional emissivity modeling and is valuable for improving the accuracy of current LST product.

地表温度是区域和全球尺度地表能量平衡和水循环等物理过程的一个关键参数，在众多研究领域都有广泛的应用，而地表发射率是制约地表温度定量化反演的一个关键参数。现有地表温度反演算法大多忽略了土壤发射率的方向性，限制了地表温度反演精度的进一步提高。本项目选择土壤为研究对象，基于已有波谱库数据和地面控制测量实验，全面分析土壤的热红外波谱特性以及影响土壤发射率的关键因子，重点选择土壤含水量和观测角度两个参数，以地面控制测量实验和辐射传输理论为手段，构建考虑含水量的土壤热红外方向发射率波谱模型，并利用地面实测数据对模型进行验证和优化，然后结合遥感地表发射率产品将模型推广到遥感像元尺度，最后将模型应用到现有常用地表温度反演算法中，并采用长时间序列地面实测数据进行验证。本项目有望在土壤发射率关键影响因子的参数化和土壤发射率方向性建模上取得突破，有望进一步提高地表温度产品精度。

地表温度是区域和全球尺度地表能量平衡和水循环等物理过程的一个关键参数，在众多研究领域都有广泛的应用，而地表发射率是制约地表温度定量化反演的一个关键参数。针对目前土壤发射率建模和地表温度反演算法存在的不足，本项目分别开展了土壤发射率控制测量以及土壤波谱发射率模型构建与地表温度反演算法研究，构建了考虑土壤含水量和观测角度的土壤波谱发射率模型，基于遥感发射率产品分析了像元尺度地表发射率角度效应对地表温度反演和上行长波辐射估算的影响，提出了基于植被指数的半经验地表温度角度归一化方法和基于ASTER全球发射率产品的高精度地表温度反演算法，并获得一批配套的地面验证实测数据。项目发表SCI论文14篇，EI论文11篇，培养博士生2名，全面完成了预订的研究目标和研究内容。本项目所取得的研究成果将对地表温度和发射率遥感反演相关的理论与实践研究有重要的参考价值。