Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model
International audience Most models simulating snow albedo assume a flat and smooth surface, neglecting surface roughness. However, the presence of macroscopic roughness leads to a systematic decrease in albedo due to two effects: (1) photons are trapped in concavities (multiple reflection effect) an...
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Online Access: | https://hal.archives-ouvertes.fr/hal-02944401 https://hal.archives-ouvertes.fr/hal-02944401/document https://hal.archives-ouvertes.fr/hal-02944401/file/tc-14-1651-2020.pdf https://doi.org/10.5194/tc-14-1651-2020 |
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ftccsdartic:oai:HAL:hal-02944401v1 2023-05-15T18:32:14+02:00 Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model Larue, Fanny Picard, Ghislain Arnaud, Laurent Ollivier, Inès Delcourt, Clément Lamare, Maxim Tuzet, François Revuelto, Jesus Dumont, Marie Institut des Géosciences de l’Environnement (IGE) Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ) Université Grenoble Alpes (UGA) Centre national de recherches météorologiques (CNRM) Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS) 2020 https://hal.archives-ouvertes.fr/hal-02944401 https://hal.archives-ouvertes.fr/hal-02944401/document https://hal.archives-ouvertes.fr/hal-02944401/file/tc-14-1651-2020.pdf https://doi.org/10.5194/tc-14-1651-2020 en eng HAL CCSD Copernicus info:eu-repo/semantics/altIdentifier/doi/10.5194/tc-14-1651-2020 hal-02944401 https://hal.archives-ouvertes.fr/hal-02944401 https://hal.archives-ouvertes.fr/hal-02944401/document https://hal.archives-ouvertes.fr/hal-02944401/file/tc-14-1651-2020.pdf doi:10.5194/tc-14-1651-2020 http://creativecommons.org/licenses/by-nd/ info:eu-repo/semantics/OpenAccess CC-BY-ND ISSN: 1994-0424 EISSN: 1994-0416 The Cryosphere https://hal.archives-ouvertes.fr/hal-02944401 The Cryosphere, Copernicus 2020, 14 (5), pp.1651-1672. ⟨10.5194/tc-14-1651-2020⟩ [SDU.OTHER]Sciences of the Universe [physics]/Other info:eu-repo/semantics/article Journal articles 2020 ftccsdartic https://doi.org/10.5194/tc-14-1651-2020 2021-12-05T01:03:48Z International audience Most models simulating snow albedo assume a flat and smooth surface, neglecting surface roughness. However, the presence of macroscopic roughness leads to a systematic decrease in albedo due to two effects: (1) photons are trapped in concavities (multiple reflection effect) and (2) when the sun is low, the roughness sides facing the sun experience an overall decrease in the local incidence angle relative to a smooth surface, promoting higher absorption, whilst the other sides have weak contributions because of the increased incidence angle or because they are shadowed (called the effective-angle effect here). This paper aims to quantify the impact of surface roughness on albedo and to assess the respective role of these two effects, with (1) observations over varying amounts of surface roughness and (2) simulations using the new rough surface ray-tracing (RSRT) model, based on a Monte Carlo method for photon transport calculation. The observations include spectral albedo (400-1050 nm) over manually created roughness surfaces with multiple geometrical characteristics. Measurements highlight that even a low fraction of surface roughness features (7 % of the surface) causes an albedo decrease of 0.02 at 1000 nm when the solar zenith angle (θ s) is larger than 50 •. For higher fractions (13 %, 27 % and 63 %), and when the roughness orientation is perpendicular to the sun, the decrease is of 0.03-0.04 at 700 nm and of 0.06-0.10 at 1000 nm. The impact is 20 % lower when roughness orientation is parallel to the sun. The observations are subsequently compared to RSRT simulations. Accounting for surface roughness improves the model observation agreement by a factor of 2 at 700 and 1000 nm (errors of 0.03 and 0.04, respectively) compared to simulations considering a flat smooth surface. The model is used to explore the albedo sensitivity to surface roughness with varying snow properties and illumination conditions. Both multiple reflections and the effective-angle effect have a greater impact with ... Article in Journal/Newspaper The Cryosphere Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) The Cryosphere 14 5 1651 1672 |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[SDU.OTHER]Sciences of the Universe [physics]/Other |
spellingShingle |
[SDU.OTHER]Sciences of the Universe [physics]/Other Larue, Fanny Picard, Ghislain Arnaud, Laurent Ollivier, Inès Delcourt, Clément Lamare, Maxim Tuzet, François Revuelto, Jesus Dumont, Marie Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model |
topic_facet |
[SDU.OTHER]Sciences of the Universe [physics]/Other |
description |
International audience Most models simulating snow albedo assume a flat and smooth surface, neglecting surface roughness. However, the presence of macroscopic roughness leads to a systematic decrease in albedo due to two effects: (1) photons are trapped in concavities (multiple reflection effect) and (2) when the sun is low, the roughness sides facing the sun experience an overall decrease in the local incidence angle relative to a smooth surface, promoting higher absorption, whilst the other sides have weak contributions because of the increased incidence angle or because they are shadowed (called the effective-angle effect here). This paper aims to quantify the impact of surface roughness on albedo and to assess the respective role of these two effects, with (1) observations over varying amounts of surface roughness and (2) simulations using the new rough surface ray-tracing (RSRT) model, based on a Monte Carlo method for photon transport calculation. The observations include spectral albedo (400-1050 nm) over manually created roughness surfaces with multiple geometrical characteristics. Measurements highlight that even a low fraction of surface roughness features (7 % of the surface) causes an albedo decrease of 0.02 at 1000 nm when the solar zenith angle (θ s) is larger than 50 •. For higher fractions (13 %, 27 % and 63 %), and when the roughness orientation is perpendicular to the sun, the decrease is of 0.03-0.04 at 700 nm and of 0.06-0.10 at 1000 nm. The impact is 20 % lower when roughness orientation is parallel to the sun. The observations are subsequently compared to RSRT simulations. Accounting for surface roughness improves the model observation agreement by a factor of 2 at 700 and 1000 nm (errors of 0.03 and 0.04, respectively) compared to simulations considering a flat smooth surface. The model is used to explore the albedo sensitivity to surface roughness with varying snow properties and illumination conditions. Both multiple reflections and the effective-angle effect have a greater impact with ... |
author2 |
Institut des Géosciences de l’Environnement (IGE) Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ) Université Grenoble Alpes (UGA) Centre national de recherches météorologiques (CNRM) Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Larue, Fanny Picard, Ghislain Arnaud, Laurent Ollivier, Inès Delcourt, Clément Lamare, Maxim Tuzet, François Revuelto, Jesus Dumont, Marie |
author_facet |
Larue, Fanny Picard, Ghislain Arnaud, Laurent Ollivier, Inès Delcourt, Clément Lamare, Maxim Tuzet, François Revuelto, Jesus Dumont, Marie |
author_sort |
Larue, Fanny |
title |
Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model |
title_short |
Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model |
title_full |
Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model |
title_fullStr |
Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model |
title_full_unstemmed |
Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model |
title_sort |
snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model |
publisher |
HAL CCSD |
publishDate |
2020 |
url |
https://hal.archives-ouvertes.fr/hal-02944401 https://hal.archives-ouvertes.fr/hal-02944401/document https://hal.archives-ouvertes.fr/hal-02944401/file/tc-14-1651-2020.pdf https://doi.org/10.5194/tc-14-1651-2020 |
genre |
The Cryosphere |
genre_facet |
The Cryosphere |
op_source |
ISSN: 1994-0424 EISSN: 1994-0416 The Cryosphere https://hal.archives-ouvertes.fr/hal-02944401 The Cryosphere, Copernicus 2020, 14 (5), pp.1651-1672. ⟨10.5194/tc-14-1651-2020⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.5194/tc-14-1651-2020 hal-02944401 https://hal.archives-ouvertes.fr/hal-02944401 https://hal.archives-ouvertes.fr/hal-02944401/document https://hal.archives-ouvertes.fr/hal-02944401/file/tc-14-1651-2020.pdf doi:10.5194/tc-14-1651-2020 |
op_rights |
http://creativecommons.org/licenses/by-nd/ info:eu-repo/semantics/OpenAccess |
op_rightsnorm |
CC-BY-ND |
op_doi |
https://doi.org/10.5194/tc-14-1651-2020 |
container_title |
The Cryosphere |
container_volume |
14 |
container_issue |
5 |
container_start_page |
1651 |
op_container_end_page |
1672 |
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