Large eddy simulation of near-surface boundary layer dynamics over patchy snow
The near-surface boundary layer over patchy snow is highly heterogeneous and dynamic. Layers of opposing stability coexist within only a few horizontal meters. Conventional experimental methods to investigate this layer suffer from limitations related to the fixed positions of eddy covariance sensor...
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Frontiers Media S.A.
2024-10-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/feart.2024.1415327/full |
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| author | Michael Haugeneder Michael Haugeneder Michael Lehning Michael Lehning Océane Hames Océane Hames Mahdi Jafari Dylan Reynolds Dylan Reynolds Rebecca Mott |
| author_facet | Michael Haugeneder Michael Haugeneder Michael Lehning Michael Lehning Océane Hames Océane Hames Mahdi Jafari Dylan Reynolds Dylan Reynolds Rebecca Mott |
| author_sort | Michael Haugeneder |
| collection | DOAJ |
| description | The near-surface boundary layer over patchy snow is highly heterogeneous and dynamic. Layers of opposing stability coexist within only a few horizontal meters. Conventional experimental methods to investigate this layer suffer from limitations related to the fixed positions of eddy covariance sensors. To overcome these difficulties, we set up a centimeter-resolution large eddy simulation of flow across an idealised transition from bare ground to snow. We force the simulation with high-frequency eddy covariance data recorded during a field campaign. We show that the model can represent the real flow by comparing it to independent eddy covariance data. However, the simulation underestimates vertical wind speed fluctuations, especially at high frequencies. Sensitivity analyses show that this is influenced by grid resolution and surface roughness representation but not much by subgrid-scale parameterization. Nevertheless, the model can reproduce the experimentally observed plumes of warm air intermittently detaching from bare ground and being advected over snow. This process is highly dynamic, with time scales of only a few seconds. We can show that the growth of a stable internal boundary layer adjacent to the snow surface can be approximated by a power law. With low wind speeds, deeper stable layers develop, while strong wind speeds limit the growth. Even close to the surface, the buoyancy fluxes are heterogeneous and driven by terrain variations, which also induce the frequent decoupling of a thin layer adjacent to the snow surface. Our simulations point the path towards generalizing point-based and aerial measurements to three dimensions. |
| format | Article |
| id | doaj-art-d3e4d6a5040a40139a23ebea68b25b4e |
| institution | OA Journals |
| issn | 2296-6463 |
| language | English |
| publishDate | 2024-10-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Earth Science |
| spelling | doaj-art-d3e4d6a5040a40139a23ebea68b25b4e2025-08-20T02:26:38ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632024-10-011210.3389/feart.2024.14153271415327Large eddy simulation of near-surface boundary layer dynamics over patchy snowMichael Haugeneder0Michael Haugeneder1Michael Lehning2Michael Lehning3Océane Hames4Océane Hames5Mahdi Jafari6Dylan Reynolds7Dylan Reynolds8Rebecca Mott9Snow and atmosphere, WSL Institute for Snow and Avalanche Research SLF, Davos, SwitzerlandLaboratory of Cryospheric Sciences, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, SwitzerlandSnow and atmosphere, WSL Institute for Snow and Avalanche Research SLF, Davos, SwitzerlandLaboratory of Cryospheric Sciences, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, SwitzerlandSnow and atmosphere, WSL Institute for Snow and Avalanche Research SLF, Davos, SwitzerlandLaboratory of Cryospheric Sciences, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, SwitzerlandSnow and atmosphere, WSL Institute for Snow and Avalanche Research SLF, Davos, SwitzerlandSnow and atmosphere, WSL Institute for Snow and Avalanche Research SLF, Davos, SwitzerlandLaboratory of Cryospheric Sciences, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, SwitzerlandSnow and atmosphere, WSL Institute for Snow and Avalanche Research SLF, Davos, SwitzerlandThe near-surface boundary layer over patchy snow is highly heterogeneous and dynamic. Layers of opposing stability coexist within only a few horizontal meters. Conventional experimental methods to investigate this layer suffer from limitations related to the fixed positions of eddy covariance sensors. To overcome these difficulties, we set up a centimeter-resolution large eddy simulation of flow across an idealised transition from bare ground to snow. We force the simulation with high-frequency eddy covariance data recorded during a field campaign. We show that the model can represent the real flow by comparing it to independent eddy covariance data. However, the simulation underestimates vertical wind speed fluctuations, especially at high frequencies. Sensitivity analyses show that this is influenced by grid resolution and surface roughness representation but not much by subgrid-scale parameterization. Nevertheless, the model can reproduce the experimentally observed plumes of warm air intermittently detaching from bare ground and being advected over snow. This process is highly dynamic, with time scales of only a few seconds. We can show that the growth of a stable internal boundary layer adjacent to the snow surface can be approximated by a power law. With low wind speeds, deeper stable layers develop, while strong wind speeds limit the growth. Even close to the surface, the buoyancy fluxes are heterogeneous and driven by terrain variations, which also induce the frequent decoupling of a thin layer adjacent to the snow surface. Our simulations point the path towards generalizing point-based and aerial measurements to three dimensions.https://www.frontiersin.org/articles/10.3389/feart.2024.1415327/fulllarge eddy simulationnear-surface boundary layerturbulencepatchy snowstable internal boundary layerbuoyancy flux |
| spellingShingle | Michael Haugeneder Michael Haugeneder Michael Lehning Michael Lehning Océane Hames Océane Hames Mahdi Jafari Dylan Reynolds Dylan Reynolds Rebecca Mott Large eddy simulation of near-surface boundary layer dynamics over patchy snow Frontiers in Earth Science large eddy simulation near-surface boundary layer turbulence patchy snow stable internal boundary layer buoyancy flux |
| title | Large eddy simulation of near-surface boundary layer dynamics over patchy snow |
| title_full | Large eddy simulation of near-surface boundary layer dynamics over patchy snow |
| title_fullStr | Large eddy simulation of near-surface boundary layer dynamics over patchy snow |
| title_full_unstemmed | Large eddy simulation of near-surface boundary layer dynamics over patchy snow |
| title_short | Large eddy simulation of near-surface boundary layer dynamics over patchy snow |
| title_sort | large eddy simulation of near surface boundary layer dynamics over patchy snow |
| topic | large eddy simulation near-surface boundary layer turbulence patchy snow stable internal boundary layer buoyancy flux |
| url | https://www.frontiersin.org/articles/10.3389/feart.2024.1415327/full |
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