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DOI	10.5194/tcd-9-3405-2015
	Measurements and modelling of snow particle size and shortwave infrared albedo over a melting Antarctic ice sheet
	Pirazzini R.; Räisänen P.; Vihma T.; Johansson M.; Tastula E.-M.
发表日期	2015
ISSN	19940432
卷号	9 期号:3
英文摘要	The albedo of a snowpack depends on the single-scattering properties of individual snow crystals, which have a variety of shapes and sizes, and are often bounded in clusters. From the point of view of optical modelling, it is essential to identify the geometric dimensions of the population of snow particles that synthetize the scattering properties of the snowpack surface. This involves challenges related to the complexity of modelling the radiative transfer in such an irregular medium, and to the difficulty of measuring microphysical snow properties. In this paper, we illustrate a method to measure the size distribution of a snow particle parameter, which roughly corresponds to the smallest snow particle dimension, from two-dimensional macro-photos of snow particles taken in Antarctica at the surface layer of a melting ice sheet. We demonstrate that this snow particle metric corresponds well to the optically equivalent effective radius utilized in radiative transfer modelling, in particular when snow particles are modelled with the droxtal shape. The surface albedo modelled on the basis of the measured snow particle metric showed an excellent match with the observed albedo when there was fresh or drifted snow at the surface. In the other cases, a good match was present only for wavelengths longer than 1.4 μm. For shorter wavelengths, our modelled albedo generally overestimated the observations, in particular when surface hoar and faceted polycrystals were present at the surface and surface roughness was increased by millimetre-scale cavities generated during melting. Our results indicate that more than just one particle metric distribution is needed to characterize the snow scattering properties at all optical wavelengths, and suggest an impact of millimetre-scale surface roughness on the shortwave infrared albedo. © Author(s) 2015.
语种	英语
来源期刊	Cryosphere Discussions
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/119871
作者单位	Finnish Meteorological Institute, Helsinki, Finland; College of Marine Science, University of South Florida, St. Petersburg, FL, United States
推荐引用方式 GB/T 7714	Pirazzini R.,Räisänen P.,Vihma T.,et al. Measurements and modelling of snow particle size and shortwave infrared albedo over a melting Antarctic ice sheet[J],2015,9(3).
APA	Pirazzini R.,Räisänen P.,Vihma T.,Johansson M.,&Tastula E.-M..(2015).Measurements and modelling of snow particle size and shortwave infrared albedo over a melting Antarctic ice sheet.Cryosphere Discussions,9(3).
MLA	Pirazzini R.,et al."Measurements and modelling of snow particle size and shortwave infrared albedo over a melting Antarctic ice sheet".Cryosphere Discussions 9.3(2015).