地物比辐射率测量方法与土壤比辐射率的变化规律研究

Surface emissivity is a main factor influencing surface temperature retrievals with remote sensed data and is an important indicator of distinguishing the types of minerals and rocks. By means of the sealing-cavity device with accurate environmental radiation control, soil emissivity in normal angle of view is measured. Using the new generation of CO2 laser and multi-angle observation device, the process of measuring directional soil emissivity is standarized, based on which, directional soil emissivity is measured. Using Fourier transform infrared (FTIR) with active radiation source of silicon-carbide, spectrum of soil emissivity is obtained. A new method of measuring spectrum of emissivity with CO2 laser and 102F FTIR is explored. On the basis of large quantities of soil emissivity under different conditions of soil type, soil component and soil water content, the following researches are carried out: (1)the relationship between soil emissivity and soil component is analyzed and a experimental model is established;(2)the process of the variation of soil emissivity with soil water content is illustrated and a method of estimating soil emissivity taking into account soil water content is developed; (3)directional and spectrum characteristics of soil emissivity under different soil conditions are illustrated. The research could provide important regular knowledge about soil emissivty and validation data for surface temperature retrieval with remote sensed data, and also could provide theoretical basis for distinguishing the types of minerals and rocks.

比辐射率是影响地表温度遥感反演精度的主要因素，是进行岩矿识别和矿物成分分析的重要指标。本研究通过对精准环境照度的控制改进黑体筒观测装置，用于观测垂直法向土壤比辐射率；利用新一代CO2激光器和多角度观测装置为核心部件设计方向比辐射率观测技术流程，实现方向比辐射率观测；利用碳化硅主动热辐射源式的傅立叶变换红外光谱仪实现比辐射率波谱的观测；同时探索利用新一代CO2激光与102F野外傅立叶变换红外光谱仪的配合观测比辐射率波谱的方法；在大量不同土壤类型，土壤成分和土壤水分的土壤比辐射率观测数据的支持下，开展比辐射率与土壤成分和土壤水分的关系研究，构建土壤成分与比辐射率的参数化模型，建立考虑土壤水分影响的比辐射率估算方法，揭示不同条件土壤的比辐射率随观测方向和波长的变化规律。为用遥感手段反演地表温度提供重要的变化规律性知识和验证数据，为比辐射率在岩矿识别和成分分析中的应用提供理论基础。

本项目在大量试验观测和仪器试制的基础上，以项目任务书为大纲按计划执行，如期开展了与项目研究内容相关的如下工作：1）黑体筒比辐射率测量方法的改进研究；2）102F傅里叶变换红外光谱仪观测比辐射率的改进研究；3）IS10室内傅里叶变换红外光谱仪观测比辐射率的改进研究；4）新一代CO2激光器与102F便携式傅立叶变换红外光谱仪配合观测比辐射率波谱的方法研究；5）基于试验的比辐射率与土壤成分的关系和波谱特征研究；6）基于试验的比辐射率与土壤水分的关系和波谱特征研究；7）考虑土壤水分的比辐射率获取方法在地表温度反演中的应用研究。本项目执行期间共获得4项发明专利，其中3项授权，1项受理；发表SCI论文9篇，发表CSCD论文2篇，审稿中CSCD论文1篇。.通过系列比辐射率测量方法的改进研究产出了4项国家发明专利，发展了比辐射率地面测量方法，提高了观测精度；基于这些发明专利，取得了有科学价值的比辐射率与土壤水分和土壤成分关系的基础数据；基于这些数据，明确了土壤发射率光谱与土壤成分的相关性，找到了土壤元素含量与土壤发射率相关性最大的特征波段，并遴选出了不同波段与发射率最相关的土壤元素；基于大量比辐射率与土壤水分的观测数据，明确了比辐射率随土壤水分的增加而增加，其中影响的最显著波段范围是3.3-5.3 μm，波段平均比辐射率干土与湿土差异大于0.2；在热红外波段，8-9.5 μm是土壤水分对比辐射率影响最大的波段，干土与湿土比辐射率差异大于0.05。另外，比辐射率随着粗糙度的增加略有增加，干土和湿土都有此规律；研究还提出了运用10.6微米单波段CO2激光器和102F红外傅里叶波谱仪获取8-14微米窗口区地物比辐射率光谱分布的新方法，并试验证明了测量思路的合理性和可行性；通过应用考虑土壤水分影响的比辐射率获取方法于地表温度的反演发现，对通用分裂窗算法地表温度反演精度提高0.4-0.8K；对单窗算法地表温度反演精度提高了1K。