面向城市场景的地表等效发射率方向性差异核驱动模型

Improving urban surface temperature inversion accuracy from remote sensing approach is facing many difficulties. The angular behavior of land surface temperature (LST) caused by heterogeneous urban surface structure is becoming a dominant limiting factor. Studies on the angular variation in effective emissivity are considered as an important way to address the angular effects and the kernel driven model shows its ability to quantify the directional effective emissivity. This project plans to construct urban scenes of different characteristics and describes the basic law that underlies the angular anisotropy from the perspective of effective emissivity. A kernel driven model will be developed to correct the angular effects of LST derived from remote sensing data. .This study includes the following: (1) We will construct a radiative transfer model and a geometric optical model to analyze driving kernels of directional effective emissivity through simplifying, simulating and generating different urban scenes. (2) We manage to construct a theoretical framework for the kernel driven model, elicit its mathematical forms and discuss its applicability and uncertainty. (3) We will propose an algorithm to address angular effects coupling the kernel driven model for effective emissivity anisotropy with the split window algorithm for retrieving directional-independent LST. A pattern to address urban surface temperature directional anisotropy will be proposed and cross-validated by using multi-angular data from geostationary satellites and multi-temporal data from polar orbiting satellites.

提升城市地表温度遥感反演的精度正面临诸多困难，其中由于复杂的城市结构形态所引发反演温度的“角度效应”，日益成为主导限制因素。地表等效发射率的方向性差异研究被认为是解决角度效应问题的重要途径，而核驱动模型则为刻画等效发射率方向性差异提供了有效手段。项目针对不同城市场景，围绕地表等效发射率，旨在阐明其方向性差异的内在规律，构建其核驱动模型，进而发展城市地表遥感反演温度的角度效应消除方法。.研究内容包括：1）通过不同城市场景简化、模拟及生成，构建城市场景热辐射传输模型和几何光学模型，揭示等效发射率方向性差异的驱动机制；2）搭建核驱动模型理论框架，构建“核”的数学表达，厘定核驱动模型的适用范围和不确定性；3）耦合等效发射率方向性差异核驱动模型与“劈窗算法”，发展角度效应消除方法。以多角度静止轨道卫星与多时间极轨卫星相结合，构建城市地表遥感反演温度的角度效应消除模式，并开展角度效应消除的交叉验证。

如何提升城市地表温度遥感反演的精度正面临诸多困难，其中之一是由于复杂的城市结构形态所引发反演温度的“角度效应”。地表等效发射率的方向性差异研究被认为是解决角度效应问题的重要途径，而核驱动模型则为刻画等效发射率方向性差异提供了有效手段。本项目完成的主要研究工作包括：（1）考虑建筑几何结构，划分地表组分类型，对地表温度日内动态变化进行参数化，进而构建等效发射率各向异性“等效光学发射率核”。（2）针对现有技术校正温度角度效应具有空间的局限性以及地形对热辐射的影响未受到重视的问题，结合已有的研究，数据和方法，提出一种普适性强的像元级“等效辐射发射率核”。（3）城市地表遥感温度的角度效应消除案例研究。以建筑材质和几何结构相对均一的法国图卢兹为例，利用地面实测数据评估了MODIS LST 在城市区域的角度效应，模拟了角度效应的日内和季节变化，证实了在城市地表开展卫星观测角度效应校正的必要性，探讨了在相对均质城市地表，开展地表温度角度效应消除的方法。.项目针对不同城市场景，围绕地表等效发射率，揭示了方向性差异的内在规律，构建了核驱动模型，发展了城市地表遥感反演温度的角度效应消除方法，促进了城市热红外遥感研究。