极轨卫星地表温度产品角度归一化方法研究

Because of the directionality of thermal infrared radiation and the stripe scanning characteristic of polar orbit satellites, the pixels observed from different polar orbit satellite data (even the same polar orbit satellite data measured within two continuous days) have different observation angles, and the retrieved land surface temperature (LST) products accordingly are not comparable, which limit significantly the applications of LST products. To address this issue, this project devotes to analyze the directional characteristics of thermal infrared radiation over pixel scale of polar orbit satellite, and to explore the impact mechanism on the directionality of thermal infrared radiation caused by different atmospheric conditions, different components of land surface types, as well as different observation geometrics. Then the project aims to develop a series of remote sensing retrieval models, including directional land surface emissivity retrieval model, land surface component temperature retrieval model, LST angular normalization model and so on. The objective of the project is to realize the angle normalization of LST products retrieved from polar orbit satellite data and produce regionally comparable and consistent LST products. Results obtained in this project can provide accurate and reliable LST products to meet the government's requirements of responding to the weather forecasting, farm yield estimation, disaster monitoring, ecological evaluation and environmental assessment and so on.

由于热红外辐射存在方向性和极轨卫星固有的条带观测扫描特性，导致利用极轨卫星数据反演的同一天不同像元或同一像元不同天的地表温度产品之间缺乏可比性，温度产品应用受到很大程度的限制。本项目通过分析极轨卫星尺度上热辐射的方向性特性，探索不同大气状况、不同组分下垫面以及不同观测几何条件等对热辐射方向性的影响机制，分别建立起具有物理意义的极轨卫星地表方向性发射率遥感反演模型、地表组分温度遥感反演模型以及地表温度产品角度归一化模型等，实现极轨卫星地表温度产品的角度归一化，从而生成具备区域可比性要求的、高质量的地表温度产品，以满足国家在气象预报、农情估产、灾情监测、生态与环境评估等方面的重大应用需求。

项目首先系统地分析了温度滞后性对热辐射方向性建模的影响，通过引入转换组分的新概念构建了考虑温度滞后性的热辐射方向性模型；接着，从热辐射自身特点出发，推导了新的几何光学核函数，并结合现有的散射核函数，构建了热辐射核驱动模型，并指出热辐射方向性效应可以由光照/阴影土壤温差、发射率角度效应以及光照/阴影植被温差3个部分进行描述；同时，结合温度日变化模型并考虑空间相关性，提出了一种改进的利用多像元和多时相数据的植被和土壤组分温度分离方法；最后，基于组分温度的分离和聚合，构建了一种切实可行的地表温度产品角度归一化方法。结果表明，所提出的角度归一化方法可以将地表温度的角度效应从1.2K降低到0.8K；校正效果对植被覆盖度（FVC）变化程度和组分发射率类型不敏感，但是会随着FVC或者土壤和植被组分温差的增加而降低。项目共发表科技论文15篇，其中SCI论文10篇，EI论文3篇，CSCD论文2篇。项目所取得的研究成果将对地表能量平衡、气候变化、蒸散发、城市热岛等诸多研究具有重要意义。