In situ continuous visible and near-infrared spectroscopy of an alpine snowpack
In situ continuous visible and near-infrared spectroscopy of an alpine snowpack
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高山积雪的原位连续可见光和近红外光谱
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
S. Morin
中科院分区：
文献类型：
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作者：
M. Dumont;L. Arnaud;G. Picard;Q. Libois;Y. Lejeune;P. Nabat;D. Voisin;S. Morin
抽象的。冬季，在科尔德港高山地区(法国阿尔卑斯山；45.30° N，5.77° E；第1325 m a.s.l.)连续测量了可见/近红外范围内的雪光谱反照率。由于强降水、快速融化事件和撒哈拉沙尘沉积暴发，这种高山积雪的演变是复杂的。这项研究强调，由此产生的光谱反照率的复杂变化可以通过以下雪面变量的变化成功地解释：雪的比表面积(SSA)、有效光吸收杂质含量、液态水的存在和坡度。在这项研究中发展的方法论理清了这些变量对雪光谱反照率的影响。雪表面液态水的存在导致反照率的光谱漂移，由此可以识别融化事件，误检率低于3.5 %。雪SSA主要影响近红外波段的光谱反照率。杂质沉积主要影响可见光区的反照率，但这种影响很大程度上依赖于雪、SSA和地表坡度。因此，我们的工作表明，对于倾斜的雪面和中到高的杂质含量，从光谱反照率估计SSA受到很大的不确定性的影响，而对杂质含量的估计也受到很大的不确定性的影响，特别是对于低于50 ng g−1黑碳当量的低值。建议的方法为从光谱反照率中恢复SSA、杂质含量、熔融事件和地表斜率开辟了途径。然而，对雪黑属性的全面准确评估将需要更多独立的现场测量，这超出了本研究的范围。然而，这一雪光谱反照率的时间序列已经为我们理解雪表面特性的演变提供了新的见解。
Abstract. Snow spectral albedo in the visible/near-infrared range has been continuously measured during a winter season at Col de Porte alpine site (French Alps; 45.30° N, 5.77° E; 1325 m a.s.l.). The evolution of such alpine snowpack is complex due to intensive precipitation, rapid melt events and Saharan dust deposition outbreaks. This study highlights that the resulting intricate variations of spectral albedo can be successfully explained by variations of the following snow surface variables: specific surface area (SSA) of snow, effective light-absorbing impurities content, presence of liquid water and slope. The methodology developed in this study disentangles the effect of these variables on snow spectral albedo. The presence of liquid water at the snow surface results in a spectral shift of the albedo from which melt events can be identified with an occurrence of false detection rate lower than 3.5 %. Snow SSA mostly impacts spectral albedo in the near-infrared range. Impurity deposition mostly impacts the albedo in the visible range but this impact is very dependent on snow SSA and surface slope. Our work thus demonstrates that the SSA estimation from spectral albedo is affected by large uncertainties for a tilted snow surface and medium to high impurity contents and that the estimation of impurity content is also affected by large uncertainties, especially for low values below 50 ng g−1 black carbon equivalent. The proposed methodology opens routes for retrieval of SSA, impurity content, melt events and surface slope from spectral albedo. However, an exhaustive accuracy assessment of the snow black properties retrieval would require more independent in situ measurements and is beyond the scope of the present study. This time series of snow spectral albedo nevertheless already provides a new insight into our understanding of the evolution of snow surface properties.