积雪性质与积雪表面双向偏振反射之间关系研究

积雪性质的变化会影响积雪的反射，从而遥感技术中可以利用反射信息的变化来确定积雪性质。由于反射过程中会产生偏振信息，在研究可见光近红外波段(350～2 500 nm)不同粒径大小积雪表面多角度反射特性的基础上，同时分析了粒径以及由干雪变成湿雪对积雪表面偏振反射特性的影响。通过野外测量结果表明，粒径大小对积雪表面偏振反射的影响在近红外波段1 500 nm附近比较明显，表现为在前向散射方向，随着粒径的增加对应的偏振度变大;这是由于在该波段附近，积雪对光的吸收很强，随着粒径的增加，吸收会变大，探测器获取的光大部分为单次散射光，而单次散射光是引起偏振信息的主要来源;在研究过程中发现从干雪变成湿雪这一过程会使偏振信息增加，这是由于湿雪表面水膜的存在，将相邻的雪粒粘连在一起，相当于使积雪粒径变大，但是这种影响主要体现在近红外波段。综上所述，将多角度偏振信息与反射信息结合可以为反演积雪性质提供可靠的方法与理论基础。

The Research of the Relationship Between Snow Properties and the Bidirectional Polarized Reflectance from Snow Surface

In the context of remote sensing, the reflectance of snow is a key factor for accurate inversion for snow properties, such as snow grain size, albedo, because of it is influenced by the change of snow properties. The polarized reflectance is a general phenomenon during the reflected progress in natural incident light. In this paper, based on the correct measurements for the multiple-angle reflected property of snow field in visible and near infrared wavelength (from 350 to 2 500 nm), the influence of snow grain size and wet snow on the bidirectional polarized property of snow was measured and analyzed. Combining the results measured in the field and previous conclusions confirms that the relation between polarization and snow grain size is obvious in infrared wavelength (at about 1 500 nm), which means the degree of polarization increasing with an increase of snow grain size in the forward scattering direction, it is because the strong absorption of ice near 1 500 nm leads to the single scattering light contributes to the reflection information obtained by the sensor; in other word, the larger grain size, the more absorption accompanying the larger polarization in forward scattering direction; we can illustrate that the change from dry snow to wet snow also influences the polarization property of snow, because of the water on the surface of snow particle adheres the adjacent particles, that means the wet snow grain size is larger than the dry snow grain size. Therefore, combining the multiple-angle polarization with reflectance will provide solid method and theoretical basis for inversion of snow properties.