Influence of grain shape on light penetration in snow
International audience The energy budget and the photochemistry of a snowpack depend greatly on the penetration of solar radiation in snow. Below the snow surface, spectral irradiance decreases exponentially with depth with a decay constant called the asymptotic flux extinction coefficient. As with...
Published in: | The Cryosphere |
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Main Authors: | , , , , , , |
Other Authors: | , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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HAL CCSD
2013
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Online Access: | https://hal.archives-ouvertes.fr/hal-03080354 https://hal.archives-ouvertes.fr/hal-03080354/document https://hal.archives-ouvertes.fr/hal-03080354/file/Libois2013_Light_Penetration_Snow.pdf https://doi.org/10.5194/tc-7-1803-2013 |
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[SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] |
spellingShingle |
[SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] Libois, Q Picard, G. France, J., Arnaud, L. Dumont, Marie Carmagnola, C., King, M. Influence of grain shape on light penetration in snow |
topic_facet |
[SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] |
description |
International audience The energy budget and the photochemistry of a snowpack depend greatly on the penetration of solar radiation in snow. Below the snow surface, spectral irradiance decreases exponentially with depth with a decay constant called the asymptotic flux extinction coefficient. As with the albedo of the snowpack, the asymptotic flux extinction coefficient depends on snow grain shape. While representing snow by a collection of spherical particles has been successful in the numerical computation of albedo, such a description poorly explains the decrease of irradiance in snow with depth. Here we explore the limits of the spherical representation. Under the assumption of geometric optics and weak absorption by snow, the grain shape can be simply described by two parameters: the absorption enhancement parameter B and the geometric asymmetry factor gG. Theoretical calculations show that the albedo depends on the ratio B/(1-gG) and the asymptotic flux extinction coefficient depends on the product B(1-gG). To understand the influence of grain shape, the values of B and gG are calculated for a variety of simple geometric shapes using ray tracing simulations. The results show that B and (1-gG) generally covary so that the asymptotic flux extinction coefficient exhibits larger sensitivity to the grain shape than albedo. In particular it is found that spherical grains propagate light deeper than any other investigated shape. In a second step, we developed a method to estimate B from optical measurements in snow. A multi-layer, two-stream, radiative transfer model, with explicit grain shape dependence, is used to retrieve values of the B parameter of snow by comparing the model to joint measurements of reflectance and irradiance profiles. Such measurements were performed in Antarctica and in the Alps yielding estimates of B between 0.8 and 2.0. In addition, values of B were estimated from various measurements found in the literature, leading to a wider range of values (1.0–9.9) which may be partially explained ... |
author2 |
Laboratoire de glaciologie et géophysique de l'environnement (LGGE) Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG) Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS) Department of Earth Sciences Egham Royal Holloway University of London (RHUL) Centre d'Etudes de la Neige (CEN) Centre national de recherches météorologiques (CNRM) Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS) Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Libois, Q Picard, G. France, J., Arnaud, L. Dumont, Marie Carmagnola, C., King, M. |
author_facet |
Libois, Q Picard, G. France, J., Arnaud, L. Dumont, Marie Carmagnola, C., King, M. |
author_sort |
Libois, Q |
title |
Influence of grain shape on light penetration in snow |
title_short |
Influence of grain shape on light penetration in snow |
title_full |
Influence of grain shape on light penetration in snow |
title_fullStr |
Influence of grain shape on light penetration in snow |
title_full_unstemmed |
Influence of grain shape on light penetration in snow |
title_sort |
influence of grain shape on light penetration in snow |
publisher |
HAL CCSD |
publishDate |
2013 |
url |
https://hal.archives-ouvertes.fr/hal-03080354 https://hal.archives-ouvertes.fr/hal-03080354/document https://hal.archives-ouvertes.fr/hal-03080354/file/Libois2013_Light_Penetration_Snow.pdf https://doi.org/10.5194/tc-7-1803-2013 |
genre |
Antarc* Antarctica The Cryosphere |
genre_facet |
Antarc* Antarctica The Cryosphere |
op_source |
ISSN: 1994-0424 EISSN: 1994-0416 The Cryosphere https://hal.archives-ouvertes.fr/hal-03080354 The Cryosphere, Copernicus 2013, 7 (6), pp.1803-1818. ⟨10.5194/tc-7-1803-2013⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.5194/tc-7-1803-2013 hal-03080354 https://hal.archives-ouvertes.fr/hal-03080354 https://hal.archives-ouvertes.fr/hal-03080354/document https://hal.archives-ouvertes.fr/hal-03080354/file/Libois2013_Light_Penetration_Snow.pdf doi:10.5194/tc-7-1803-2013 |
op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.5194/tc-7-1803-2013 |
container_title |
The Cryosphere |
container_volume |
7 |
container_issue |
6 |
container_start_page |
1803 |
op_container_end_page |
1818 |
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ftccsdartic:oai:HAL:hal-03080354v1 2023-05-15T13:54:51+02:00 Influence of grain shape on light penetration in snow Libois, Q Picard, G. France, J., Arnaud, L. Dumont, Marie Carmagnola, C., King, M. Laboratoire de glaciologie et géophysique de l'environnement (LGGE) Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG) Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS) Department of Earth Sciences Egham Royal Holloway University of London (RHUL) Centre d'Etudes de la Neige (CEN) Centre national de recherches météorologiques (CNRM) Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS) Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS) 2013 https://hal.archives-ouvertes.fr/hal-03080354 https://hal.archives-ouvertes.fr/hal-03080354/document https://hal.archives-ouvertes.fr/hal-03080354/file/Libois2013_Light_Penetration_Snow.pdf https://doi.org/10.5194/tc-7-1803-2013 en eng HAL CCSD Copernicus info:eu-repo/semantics/altIdentifier/doi/10.5194/tc-7-1803-2013 hal-03080354 https://hal.archives-ouvertes.fr/hal-03080354 https://hal.archives-ouvertes.fr/hal-03080354/document https://hal.archives-ouvertes.fr/hal-03080354/file/Libois2013_Light_Penetration_Snow.pdf doi:10.5194/tc-7-1803-2013 info:eu-repo/semantics/OpenAccess ISSN: 1994-0424 EISSN: 1994-0416 The Cryosphere https://hal.archives-ouvertes.fr/hal-03080354 The Cryosphere, Copernicus 2013, 7 (6), pp.1803-1818. ⟨10.5194/tc-7-1803-2013⟩ [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] info:eu-repo/semantics/article Journal articles 2013 ftccsdartic https://doi.org/10.5194/tc-7-1803-2013 2021-10-24T00:10:28Z International audience The energy budget and the photochemistry of a snowpack depend greatly on the penetration of solar radiation in snow. Below the snow surface, spectral irradiance decreases exponentially with depth with a decay constant called the asymptotic flux extinction coefficient. As with the albedo of the snowpack, the asymptotic flux extinction coefficient depends on snow grain shape. While representing snow by a collection of spherical particles has been successful in the numerical computation of albedo, such a description poorly explains the decrease of irradiance in snow with depth. Here we explore the limits of the spherical representation. Under the assumption of geometric optics and weak absorption by snow, the grain shape can be simply described by two parameters: the absorption enhancement parameter B and the geometric asymmetry factor gG. Theoretical calculations show that the albedo depends on the ratio B/(1-gG) and the asymptotic flux extinction coefficient depends on the product B(1-gG). To understand the influence of grain shape, the values of B and gG are calculated for a variety of simple geometric shapes using ray tracing simulations. The results show that B and (1-gG) generally covary so that the asymptotic flux extinction coefficient exhibits larger sensitivity to the grain shape than albedo. In particular it is found that spherical grains propagate light deeper than any other investigated shape. In a second step, we developed a method to estimate B from optical measurements in snow. A multi-layer, two-stream, radiative transfer model, with explicit grain shape dependence, is used to retrieve values of the B parameter of snow by comparing the model to joint measurements of reflectance and irradiance profiles. Such measurements were performed in Antarctica and in the Alps yielding estimates of B between 0.8 and 2.0. In addition, values of B were estimated from various measurements found in the literature, leading to a wider range of values (1.0–9.9) which may be partially explained ... Article in Journal/Newspaper Antarc* Antarctica The Cryosphere Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) The Cryosphere 7 6 1803 1818 |