气候变化领域集成服务门户(CCPortal): Parameterizing anisotropic reflectance of snow surfaces from airborne digital camera observations in Antarctica

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DOI	10.5194/tc-14-3959-2020
	Parameterizing anisotropic reflectance of snow surfaces from airborne digital camera observations in Antarctica
	Carlsen T.; Birnbaum G.; Ehrlich A.; Helm V.; Jäkel E.; Schäfer M.; Wendisch M.
发表日期	2020
ISSN	19940416
起始页码	3959
结束页码	3978
卷号	14 期号:11
英文摘要	The surface reflection of solar radiation comprises an important boundary condition for solar radiative transfer simulations. In polar regions above snow surfaces, the surface reflection is particularly anisotropic due to low Sun elevations and the highly anisotropic scattering phase function of the snow crystals. The characterization of this surface reflection anisotropy is essential for satellite remote sensing over both the Arctic and Antarctica. To quantify the angular snow reflection properties, the hemispherical-directional reflectance factor (HDRF) of snow surfaces was derived from airborne measurements in Antarctica during austral summer in 2013/14. For this purpose, a digital 180 fish-eye camera (green channel, 490-585 nm wavelength band) was used. The HDRF was measured for different surface roughness conditions, optical-equivalent snow grain sizes, and solar zenith angles. The airborne observations covered an area of around 1000 km × 1000 km in the vicinity of Kohnen Station (750′ S, 04′ E) at the outer part of the East Antarctic Plateau. The observations include regions with higher (coastal areas) and lower (inner Antarctica) precipitation amounts and frequencies. The digital camera provided upward, angular-dependent radiance measurements from the lower hemisphere. The comparison of the measured HDRF derived for smooth and rough snow surfaces (sastrugi) showed significant differences, which are superimposed on the diurnal cycle. By inverting a semi-empirical kernel-driven bidirectional reflectance distribution function (BRDF) model, the measured HDRF of snow surfaces was parameterized as a function of solar zenith angle, surface roughness, and optical-equivalent snow grain size. This allows a direct comparison of the HDRF measurements with the BRDF derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite product MCD43. For the analyzed cases, MODIS observations (545-565 nm wavelength band) generally underestimated the anisotropy of the surface reflection. The largest deviations were found for the volumetric model weight fvol (average underestimation by a factor of 10). These deviations are likely linked to short-term changes in snow properties. © 2020 Author(s).
英文关键词	airborne survey; digitization; MODIS; observational method; parameterization; remote sensing; satellite data; surface reflectance
语种	英语
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202042
作者单位	Leipzig Institute for Meteorology, University of Leipzig, Leipzig, Germany; Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany; Department of Geosciences, University of Oslo, Oslo, Norway
推荐引用方式 GB/T 7714	Carlsen T.,Birnbaum G.,Ehrlich A.,et al. Parameterizing anisotropic reflectance of snow surfaces from airborne digital camera observations in Antarctica[J],2020,14(11).
APA	Carlsen T..,Birnbaum G..,Ehrlich A..,Helm V..,Jäkel E..,...&Wendisch M..(2020).Parameterizing anisotropic reflectance of snow surfaces from airborne digital camera observations in Antarctica.Cryosphere,14(11).
MLA	Carlsen T.,et al."Parameterizing anisotropic reflectance of snow surfaces from airborne digital camera observations in Antarctica".Cryosphere 14.11(2020).