Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps
Over Saint-Sorlin Glacier in the French Alps (45° N, 6.1° E; ∼ 3 km 2 ) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to large-scale forcing. We use...
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ftdoajarticles:oai:doaj.org/article:dc461101180149ce87f41f41b73667e3 2023-05-15T18:32:30+02:00 Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps M. Litt J.-E. Sicart D. Six P. Wagnon W. D. Helgason 2017-04-01T00:00:00Z https://doi.org/10.5194/tc-11-971-2017 https://doaj.org/article/dc461101180149ce87f41f41b73667e3 EN eng Copernicus Publications http://www.the-cryosphere.net/11/971/2017/tc-11-971-2017.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 1994-0416 1994-0424 doi:10.5194/tc-11-971-2017 https://doaj.org/article/dc461101180149ce87f41f41b73667e3 The Cryosphere, Vol 11, Iss 2, Pp 971-987 (2017) Environmental sciences GE1-350 Geology QE1-996.5 article 2017 ftdoajarticles https://doi.org/10.5194/tc-11-971-2017 2022-12-31T11:38:54Z Over Saint-Sorlin Glacier in the French Alps (45° N, 6.1° E; ∼ 3 km 2 ) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to large-scale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the glacier's atmospheric surface layer. We evaluate the turbulent fluxes with the eddy-covariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the glacier, weak katabatic flows with a wind-speed maximum at low height (2–3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. Radiative fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the glacier flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of large-scale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed melt to be able to recommend one turbulent flux calculation method over ... Article in Journal/Newspaper The Cryosphere Directory of Open Access Journals: DOAJ Articles The Cryosphere 11 2 971 987 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
spellingShingle |
Environmental sciences GE1-350 Geology QE1-996.5 M. Litt J.-E. Sicart D. Six P. Wagnon W. D. Helgason Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
Over Saint-Sorlin Glacier in the French Alps (45° N, 6.1° E; ∼ 3 km 2 ) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to large-scale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the glacier's atmospheric surface layer. We evaluate the turbulent fluxes with the eddy-covariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the glacier, weak katabatic flows with a wind-speed maximum at low height (2–3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. Radiative fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the glacier flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of large-scale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed melt to be able to recommend one turbulent flux calculation method over ... |
format |
Article in Journal/Newspaper |
author |
M. Litt J.-E. Sicart D. Six P. Wagnon W. D. Helgason |
author_facet |
M. Litt J.-E. Sicart D. Six P. Wagnon W. D. Helgason |
author_sort |
M. Litt |
title |
Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps |
title_short |
Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps |
title_full |
Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps |
title_fullStr |
Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps |
title_full_unstemmed |
Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps |
title_sort |
surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the french alps |
publisher |
Copernicus Publications |
publishDate |
2017 |
url |
https://doi.org/10.5194/tc-11-971-2017 https://doaj.org/article/dc461101180149ce87f41f41b73667e3 |
genre |
The Cryosphere |
genre_facet |
The Cryosphere |
op_source |
The Cryosphere, Vol 11, Iss 2, Pp 971-987 (2017) |
op_relation |
http://www.the-cryosphere.net/11/971/2017/tc-11-971-2017.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 1994-0416 1994-0424 doi:10.5194/tc-11-971-2017 https://doaj.org/article/dc461101180149ce87f41f41b73667e3 |
op_doi |
https://doi.org/10.5194/tc-11-971-2017 |
container_title |
The Cryosphere |
container_volume |
11 |
container_issue |
2 |
container_start_page |
971 |
op_container_end_page |
987 |
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1766216620193087488 |