Effective UV surface albedo of seasonally snow-covered lands
Effective UV surface albedo of seasonally snow-covered lands
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DOI：
10.5194/acp-7-2759-2007
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发表时间：
2007-01-01
影响因子：
6.3
通讯作者：
Manninen, T.
中科院分区：
文献类型：
--
作者：
Tanskanen, A.;Manninen, T.
在紫外线波长下，大多数自然表面的反射率都很小，只有雪和冰例外。因此，积雪是基于辐射传输模型的各种应用的主要挑战。这项工作的目的是确定特征有效的紫外线范围内的各种土地覆盖类型的表面覆盖时，积雪。首先选取1 × 1度的样区，根据马里兰州的8 km全球土地覆盖分类产品，样区主要包含一种土地覆盖类型的亚像元，根据USGS的HYDRO 1 K坡度数据，样区的平均坡度小于2度;根据NSIDC北方每周积雪数据，样本区域在三月份有积雪。接下来，我们从Nimbus-7 TOMS Lambertian等效反射率数据中生成1 × 1度网格化360 nm表面反射率数据，并使用它们来构建每种土地覆盖类型的特征有效表面反射率分布。由此产生的分布表明，每一种土地覆盖类型的经验，一个特征范围内的表面覆盖值时，被雪覆盖。这一结果是由植被向上延伸到积雪之外，掩盖了明亮的积雪覆盖的表面。
At ultraviolet wavelengths the albedo of most natural surfaces is small with the striking exception of snow and ice. Therefore, snow cover is a major challenge for various applications based on radiative transfer modelling. The aim of this work was to determine the characteristic effective UV range surface albedo of various land cover types when covered by snow. First we selected 1 by 1 degree sample regions that met three criteria: the sample region contained dominantly subpixels of only one land cover type according to the 8 km global land cover classification product from the University of Maryland; the average slope of the sample region was less than 2 degrees according to the USGS's HYDRO1K slope data; the sample region had snow cover in March according to the NSIDC Northern Hemisphere weekly snow cover data. Next we generated 1 by 1 degree gridded 360 nm surface albedo data from the Nimbus-7 TOMS Lambertian equivalent reflectivity data, and used them to construct characteristic effective surface albedo distributions for each land cover type. The resulting distributions showed that each land cover type experiences a characteristic range of surface albedo values when covered by snow. The result is explained by the vegetation that extends upward beyond the snow cover and masks the bright snow covered surface.