Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2,...
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Transcript of Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2,...
![Page 1: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/1.jpg)
Terrain and drift influences on snow surface aerodynamics
A. Clifton1, K. C. Leonard1, C. Manes2, M. Lehning1.
1. SLF Davos, Switzerland2. Politecnico di Torino, Turin, Italy
AGU Fall Meeting 2010C11C-02
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Surface aerodynamics
• Interaction of boundary layer and surface
• Log law framework– Friction velocity (m/s)– Roughness length (m)
0.5 1 1.5 2 2.5 3 3.5 4 4.50
0.5
1
1.5
2
2.5
0.3 m/s, 1 mmIncreased friction velocity (0.5 m/s)Increased roughness (10 mm)Both increase (0.5 m/s, 10 mm)
Speed [m/s]
Z [m]
![Page 3: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/3.jpg)
Relevant processes
Anything that alters momentum transfer• Drift• Crystal structure• Snow metamorphosis• Surface forms• Local terrain
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Wind tunnel measurements
![Page 5: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/5.jpg)
Wind tunnel measurements
![Page 6: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/6.jpg)
Wind tunnel measurements
Clifton, A., Rüedi, J.-D., Lehning, M. (2006).Snow saltation threshold measurements in a drifting snow wind tunnel.J. Glaciol., 52(179), 585-596. DOI: 10.3189/172756506781828430
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Alpine test site measurements
• Fluxes of momentum, heat and water vapour– Sonic anemometer and
fast hygrometer– Concurrent surface
observations– 3 months of
observations– 5m measurement height
Stössel, F., M. Guala, C. Fierz, C. Manes, and M. Lehning (2010)Micrometeorological and morphological observations of surface hoar dynamics on a mountain snow cover.Water Resour. Res., 46, W04511. DOI: 10.1029/2009WR008198.
![Page 8: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/8.jpg)
Alpine test site measurements
• Fluxes of momentum, heat and water vapour– Sonic anemometer and
fast hygrometer– Concurrent surface
observations– 3 months of
observations– 5m measurement height
Davos 3 km
Stössel, F., M. Guala, C. Fierz, C. Manes, and M. Lehning (2010).Micrometeorological and morphological observations of surface hoar dynamics on a mountain snow cover.Water Resour. Res., 46, W04511. DOI: 10.1029/2009WR008198.
![Page 9: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/9.jpg)
Alpine test site measurements
• Fluxes of momentum, heat and water vapour– Sonic anemometer and
fast hygrometer– Concurrent surface
observations– 3 months of
observations– 5m measurement height
Davos 3 km
Stössel, F., M. Guala, C. Fierz, C. Manes, and M. Lehning (2010).Micrometeorological and morphological observations of surface hoar dynamics on a mountain snow cover.Water Resour. Res., 46, W04511. DOI: 10.1029/2009WR008198.
![Page 10: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/10.jpg)
Williams Field, Antarctica
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Williams Field, Antarctica
Commercial widget counter
York U. particle counter(P. Taylor)
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Williams Field, AntarcticaWillie Field AWSAntarctic Automatic Weather Station Program AMRC, SSEC, UW-Madison
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Williams Field, Antarctica
![Page 14: Terrain and drift influences on snow surface aerodynamics A. Clifton 1, K. C. Leonard 1, C. Manes 2, M. Lehning 1. 1.SLF Davos, Switzerland 2.Politecnico.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649d2e5503460f94a05399/html5/thumbnails/14.jpg)
Role of snow structure
Clifton, A., C. Manes, J.-D. Ruedi, M. Guala, and M. Lehning (2008)On shear-driven ventilation of snow. Boundary-Layer Meteorol., 126, 249-261.
DOI: 10.1007/s10546-007-9235-0.
Images courtesy M. Schneebeli, SLF
1 mm
New snow Polyester foam
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Results
Wind tunnel, without drift
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Results
Hydraulically smooth wall
Wind tunnel (no drift)
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Results
Wind tunnel, sustained drift
Wind tunnel (no drift)
Smooth wall
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Results
Drifting sand, soil, waves over open water (Owen, 1960)
Wind tunnel (no drift)
Smooth wall
Wind tunnel (drift)
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Results
William Field, without drift
Wind tunnel (no drift)
Smooth wall
Wind tunnel (drift)
Drifting sandand soil
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Results
Williams Field, with sustained drift(neutral conditions only)
Wind tunnel (no drift)
Smooth wall
Wind tunnel (drift)
Drifting sandand soil
Williams Field(no drift)
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Results
Alpine test site, all data(neutral conditions & NW flows only)
Wind tunnel (no drift)
Smooth wall
Wind tunnel (drift)
Drifting sandand soil
Williams Field(no drift)
Williams Field (drift)
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Results
Revised Davenport ClassificationDavenport (2000)
Wind tunnel (no drift)
Smooth wall
Wind tunnel (drift)
Drifting sandand soil
Williams Field(no drift)
Williams Field (drift)
Alpine Site(all data)
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ResultsDavenport
Classification
Wind tunnel (no drift)
Smooth wall
Wind tunnel (drift)
Drifting sandand soil
Williams Field(no drift)
Williams Field (drift)
Alpine Site(all data)
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Conclusions
• Log law is a useful analogy near the ground
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Conclusions
• Log law is a useful analogy near the ground• Roughness length of ‘snow’ is a function of– Friction velocity– Drift rates (increase or decrease)– Surface features (increase)– Fetch (increase)
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Conclusions
• Log law is a useful analogy near the ground• Roughness length of ‘snow’ is a function of– Friction velocity– Drift rates (increase or decrease)– Surface features (increase)– Fetch (increase)
• Next steps– Wind and drift profiles coupled with surface
characterization