热红外与微波辐射差异及关联研究

The applications of remote sensing by combining thermal infrared with microwave remote sensing are limited due to the difference between thermal infrared surface temperature and microwave effective temperature as well as the response difference of surface parameters between thermal infrared and microwave band. In order to realize that temperature products from microwave remote sensing can compensate temperature products from thermal infrared remote sensing to obtain temperature products of times series, or temperature products from thermal infrared remote sensing are made as known inputs of algorithms of retrieval of soil moisture by passive microwave remote sensing, or thermal infrared remote sensing is combined with passive microwave remote sensing to retrieve surface parameters, this study aims to develop the study of the thermal radiation difference and correlation of soil between thermal infrared and microwave band from the ground-based measurements and the simulating data. The influence of soil temperature and moisture profiles under the clear and non-clear sky conditions on microwave radiance is analyzed combining the simultaneous heat and water (SHAW) model , the ground-based measurements of soil and some microwave multi-layer soil models. Furthermore, the difference of microwave effective temperature and thermal infrared surface temperature under the clear and non-clear sky conditions. The relationship between them is tried to be constructed. Lastly, joint simulation of thermal infrared and microwave directional radiance of soil is studied on the basis of this research and by introducing thermal infrared and microwave soil emissivity models. The radiance difference between thermal infrared and microwave band is analyzed. And the results will be validated by the ground-based measurements by combining thermal imager and microwave radiometer.

由于土壤热红外皮肤温度与微波等效温度之间存在差异，土壤参数对土壤热红外发射率与微波发射率之间的响应差异而限制了热红外与微波的联合应用，比如微波温度数据弥补热红外温度数据获取时间序列的地表温度数据产品、热红外温度作为微波土壤水分反演中的已知输入量或协同热红外与微波遥感反演地表参数等方面的应用。本项目以地面实验数据及模型模拟数据作为数据源，从机理上开展土壤热红外与微波辐射差异及关联研究工作。结合土壤水热传导模型，土壤实测数据及几种不同的微波土壤分层模型，分析晴空及非晴空条件下土壤温湿廓线对微波辐射的影响，进而分析晴空及非晴空条件下土壤热红外皮肤温度与土壤微波等效温度的差异，并尝试建立起两者的关联。在此研究基础上结合热红外及微波土壤发射率模型进行裸土热红外与微波的辐射的联合模拟，分析微波与热红外的辐射差异，并采用热红外与微波的地基野外联合观测进行验证，进一步探讨联合两者反演土壤温湿廓线的可行性。

遥感技术具有快速便捷地获取大范围面上数据的优势，是区域和全球地表研究的重要手段。由于电磁波传播的色散特性，随着电磁波的波长或频率变化，电磁波对地物的各种物理化学特性及几何结构的敏感性存在差异，同时，电磁波的探测深度有差异。电磁波波长较短时，其散射和辐射特性主要由地物表面的几何特性及各种物理化学特性决定（如在光学波段）；波长较长时，其散射和辐射特性不仅与地物表面的几何特性及各种物理化学特性有关，地物体内部的各种物理化学特性也对其有影响（如微波波段）。通过对地表进行参数化来定量地构建电磁波与地物的相互作用，从而进一步服务于基于遥感手段的参数化反演。本项目以正演模型的研究为出发点，一点一点去探讨光学与微波在物理机理上的差异性并为反演提供理论基础，主要实现的工作有：改进了Wang-Schmugge土壤半经验介电模型，为之后的微波研究提供土壤介电常数模型；从机理上初步分析了晴空条件下，红外皮肤温度与微波等效温度的差异性，为之后的深入研究提供了理论基础；结合热红外及微波土壤发射率模型进行裸土微波与热红外的热辐射的联合模拟，分析微波与热红外的热辐射差异性；针对玉米作物，分析了玉米叶片形状特征及叶倾角分布对玉米微波辐射的影响。