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Spectral signatures of submicron scale light-absorbing impurities in snow and ice using hyperspectral microscopy


Dal Farra, Anna; Kaspari, Susan; Beach, James; Bucheli, Thomas D; Schaepman, Michael E; Schwikowski, Margit (2018). Spectral signatures of submicron scale light-absorbing impurities in snow and ice using hyperspectral microscopy. Journal of Glaciology, 64(245):377-386.

Abstract

Light-absorbing impurities (LAI) can darken snow and ice surfaces, reduce snow/ice albedo and accelerate melt. Efforts to allocate the relative contribution of different LAI to snow/ice albedo reductions have been limited by uncertainties in the optical properties of LAI. We developed a new method to measure LAI spectral reflectance at the submicron scale by modifying a Hyperspectral Imaging Microscope Spectrometer (HIMS). We present the instrument's internal calibration, and the overall small influence of a particle's orientation on its measured reflectance spectrum. We validated this new method through the comparison with a field spectroradiometer by measuring different standard materials. Measurements with HIMS at the submicron scale and the bulk measurements of the same standard materials with the field spectroradiometer are in good agreement with an average deviation between the spectra of 3.2% for the 400–1000 nm wavelength range. The new method was used (1) to identify BC (black carbon), mineral dust including hematite and the humic substances present in an environmental sample from Plaine Morte glacier and (2) to collect the individual reflectance spectra of each of these types of impurity. The results indicate that this method is applicable to heterogeneous samples such as the LAI found in snow and ice.

Abstract

Light-absorbing impurities (LAI) can darken snow and ice surfaces, reduce snow/ice albedo and accelerate melt. Efforts to allocate the relative contribution of different LAI to snow/ice albedo reductions have been limited by uncertainties in the optical properties of LAI. We developed a new method to measure LAI spectral reflectance at the submicron scale by modifying a Hyperspectral Imaging Microscope Spectrometer (HIMS). We present the instrument's internal calibration, and the overall small influence of a particle's orientation on its measured reflectance spectrum. We validated this new method through the comparison with a field spectroradiometer by measuring different standard materials. Measurements with HIMS at the submicron scale and the bulk measurements of the same standard materials with the field spectroradiometer are in good agreement with an average deviation between the spectra of 3.2% for the 400–1000 nm wavelength range. The new method was used (1) to identify BC (black carbon), mineral dust including hematite and the humic substances present in an environmental sample from Plaine Morte glacier and (2) to collect the individual reflectance spectra of each of these types of impurity. The results indicate that this method is applicable to heterogeneous samples such as the LAI found in snow and ice.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:1 June 2018
Deposited On:04 Jan 2019 17:14
Last Modified:04 Jan 2019 17:16
Publisher:International Glaciological Society
ISSN:0022-1430
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1017/jog.2018.29

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