积雪直接影响地表能量平衡和气候变化,与人类生产、生活息息相关,运用热红外偏振技术对新雪的发射光谱特性进行研究,可为热红外遥感监测雪的热辐射偏振特性定量研究提供基础,对加深对全球变暖理解及制定相应对策等具有重要意义.研究结果表明:波段对新雪热红外偏振特性影响很大,其偏振辐亮度(L)表现为:LCH1>LCH3>LCH4>LCH2,偏振亮温(T)表现为:TCH4>TCH1>TCH2>TCH3,在探测角50°偏振角90°处出现最大值而在探测角30°偏振角75°处存在最小值,利用CH3偏振亮温数据分析新雪热辐射偏振特性效果更优.探测角对新雪的偏振亮温影响极其显著,表现为:T10P30>P40>P20>P10>P50.偏振角对新雪亮温影响呈线性关系,在0~135°范围,每单位偏振角偏振亮温增加约0.003 ℃,这为新雪偏振亮温预测提供可能,在研究探测角对新雪偏振亮温影响时可忽略波段造成的差异.相对方位角对新雪的热辐射偏振特性影响不显著,这主要是由物质表面粗糙程度与组织结构差异导致,利用热红外偏振度对新雪的理化特性监测具有重要作用.

Snow can directly affect the surface energy balance and climate change and has a significant impact on human life and production.It is therefore of great significance to study the fresh snow emission spectroscopy properties by using the thermal infrared Polarization technique.This can provide a basis for quantitative thermal infrared remote sensing monitoring of snow as well as a deeper understanding of global warming and appropriate countermeasures.This paper focuses on the investigation of the thermal infrared polarization properties of the fresh snow.The results show that the thermal emissive polarization properties of fresh snow depend significantly on the wavelengths(channels) and view angles used to measure them.Four channels are considered in this study,their spectral response ranges are 8~14 μm for channel 1(CH1),11.5~12.5 μm for channel 2(CH2),10.3~11.5 μm for channel 3(CH3) and 8.2~9.2 μm for channel 4(CH4).The snow polarized radiance(L) and its polarized brightness temperature(T) manifest as LCH1>LCH3>LCH4>LCH2 and TCH4>TCH1>TCH2>TCH3,respectively,while the degree of polarization(P) manifests as P0>P30>P40>P20>P10>P50 where the subscript of P denotes the view angle.The maximum of both L and T occurs at the view angle of 50 degree and polarization angle of 90 degree while their minimum appears at the view angle of 30 degree and polarization angle of 75 degree for each channel.In addition,the results show that:CH3 is more appropriate for better investigation of the emissive polarization properties of snow.Linear relationship is found between the fresh snow polarized T and the polarization angle with the coefficient of determination larger than 0.77 for all four channels.The polarized brightness temperature of the fresh snow is found to be increased about 0.003 K per polarization angle within 0~135 degree.The degree of polarization of snow is almost independent of the channels we used(CH1 to CH4).The snow emissive polarization is isotropic and the relative azimuth view angle has no significant impact on the snow emissive polarization properties.The impact of the polarization angle may be neglected if the investigation of the relative azimuth view angle on the fresh snow thermal emissive polarization is conducted.The difference of the fresh snow emissive polarization properties mainly comes from the snow surface roughness and structure.