航空遥感数据典型自然下垫面偏振特性分析

Polarization properties of typical underlying nature surface based on airborne remote sensing data

对于航空航天大气偏振遥感来说,下垫面偏振辐射噪声影响扣除至关重要。本文基于航空偏振遥感数据,探讨了典型自然下垫面对可见光及短波红外波段偏振敏感性。研究发现,在可见光波段与短波红外(2250 nm)波段,植被下垫面偏振反射率线性拟合斜率都接近1,相关系数大于0.95,表明植被偏振反射率对光谱波段不敏感。比较分析了平静水面和存在耀光水面在670 nm和2250 nm两波段的偏振特性,存在耀光的水面其偏振反射率大约是平静水面的3倍。此外,在实验室测量了红砂土和河沙土的偏振反射率,偏振反射率随波段的改变量很小,其与波段的线性拟合斜率仅为10-5量级,说明两者的偏振反射率对波段很不敏感。因此,利用典型自然下垫面在可见和短波红外波段的偏振反射特性,将能够有效进行地气解耦,提高大气偏振遥感精度。

For airborne or satellite polarimetrie atmospheric detection, the reflected signal of the underlying surface is a noise that should be considered. This signal affects the retrieval precision of aerosol parameters. Therefore, research on the polarized reflected property of underlying surface is crucial for earth-atmosphere decoupling. Such a research can improve the precision of the aerosol optical depth retrieval. To design two fly height （ i. e. , 3000 m and 480 m） airborne experiments, the measurement data of the underlying nature surface （ i. e. , vegetation and water） are obtained. In addition, the polarimetric reflected data of the soil are measured in the laboratory. Combining with the theory of polarized radiative transfer and the law of Fresnel, the polarized reflected characteristic is analyzed to determine the polarized reflected characteristics of calm and glitter waters based on micro facet theory. The curve of the polarized reflectance of vegetation and soil slightly changes at different bands, and the linear fitting slope of the polarized reflectance of both visible and infrared bands （2250 nm） is close to 1. The correlation coefficient is 0.95, and the polarized reflectance of vegetation is not sensitive to the band. Comparative analysis of the polarization properties of calm and glitter waters is conducted at 670 nm and 2250 rim. The polarized reflectance of glitter water is approximately two times larger than that of calm water. This phenomenon agrees well with Fresnel theory. Finally, the polarized reflectance of red and river sandy soils is not sensitive to the band, and the linear fitting slope is only at the 10^-5 level. Analysis of airborne-polarized remote sensing data of underlying nature surface shows that the polarized reflectance of vegeta- tion is not sensitive to the band, which can use the polarized reflectance of the 2250 nm band to express the polarized reflectance of 670 nm and 1610 nm for the vegetation and soil surface. The polarized reflectance of glitter water is approximately two times larger than that of calm water. The polarized reflectance of water is changed with acute geometric conditions. The research on the polarized property of underlying nature surface efficiently decouples atmosphere-surface and improves the retrieval precision of aerosol parameters.