遥感反演地表温度的角度归一化方法研究

Accurate acquisition of land surface temperature (LST) from remote sensing data is crucial for the researches such as earth’s material and energy exchanges, water and energy cycles, global changes and so on. Because of the differences of components’ temperatures and proportions at different viewing directions, the LST at pixel always presents an angular variation, which reduces the comparability of the LST products retrieved from remote sensing data observed at different directions and consequently limits the applications of LST in some relative domains.. On the basis of the principle of LST retrieval methods from remote sensing data, this study aims at the angular normalization (i.e., to retrieve the LST at nadir direction) of LST by making full use of the spatio-temporal and spectral information included in the used data. With the considerations of two important factors, components’ temperature differences and fraction of vegetation cover that cause the angular variation of LST, this study will start with the modelling of the directional thermal radiation of land surface, and then develop a physics-based model to achieve angular normalization of LST by using two-channel thermal infrared data observed at two times (daytime and nighttime). With the above work, the study will finally establish an operational method that does not need much data input to finish the angular normalization of LST, and provide some technical supports for the future generation of angular-corrected LST products, and furthermore improve the application of LST in different domains.

准确获取地表温度信息是地表过程物质与能量交换、水热循环及其全球变化等研究的关键环节。由于像元组分温差与组分比例的影响，像元尺度地表温度往往表现出一定的方向性，从而在理论上降低了由不同方向观测数据反演的地表温度产品之间的可比性，严重限制了地表温度产品的实际应用。. 本研究从地表温度角度效应这一关键问题出发，在分析现有地表温度遥感反演理论的基础上，把握组分温差与植被覆盖度对地表温度角度效应的主导因素，构建地表方向性热辐射的参数化模型，充分利用时空信息与光谱信息发展从双时相双通道热红外遥感数据进行地表温度角度归一化(即获取垂直方向上的地表温度)的物理模型，并实现物理模型的实际运用与验证。将最终形成一套操作性强、输入数据少的地表温度角度归一化技术体系，为未来业务化生产角度归一化后的地表温度产品提供技术支撑，以促进不同地表温度产品的可比性及其在各个领域的广泛应用。

地表温度是区域与全球尺度上地表过程的关键参数与重要驱动力，是研究地表物质与能量平衡、全球变化等领域不可或缺的参数之一。利用可见光、热红外数据以及地表分类产品，本研究首先发展了地表温度遥感反演的新算法；基于“景合成”概念建立了模拟冠层的方向性热辐射新模型，并在此基础上初步探索了核驱动BRDF模型在热红外领域的适用性，提出了利用多角度热红外数据进行地表温度角度归一化的最小角度需求，并运用于实际数据中进行验证；比较分析了描述冠层高方向性发射率的四个参数化模型（2个BRDF模型与2个间隙率模型）的优缺点，更新了反映冠层内部散射作用的腔体效应因子，建立了方向性发射率参数化系数先验知识；发展了基于双时相双通道数据的地表温度角度归一化物理模型，并在研究区实现地表温度的角度归一化。本项目的研究工作为未来进一步开展地表热辐射的方向性建模与地表温度的角度归一化提供了重要参考。