Aerodynamic Roughness Length of Fresh Snow

Christof Gromke; Costantino Manes; Benjamin Walter; Michael Lehning; Michele Guala

doi:10.1007/s10546-011-9623-3

Aerodynamic Roughness Length of Fresh Snow

Christof Gromke, Costantino Manes, Benjamin Walter, Michael Lehning, Michele Guala

Civil, Environmental, and Geo- Engineering

Research output: Contribution to journal › Article › peer-review

38 Scopus citations

Abstract

This study presents the results from a series of wind-tunnel experiments designed to investigate the aerodynamic roughness length z₀ of fresh snow under no-drift conditions. A two-component hot-film anemometer was employed to obtain vertical profiles of velocity statistics in a zero pressure gradient turbulent boundary layer for flow over naturally deposited snow surfaces. The roughness of these snow surfaces was measured by means of digital photography to capture characteristic length scales that can be related to z₀. Our results show that, under aerodynamically rough conditions, the mean value of the roughness length for fresh snow is 〈z₀〉=0.24 mm with a standard deviation σ(z₀) = 0.05 mm. In this study, we show that variations in z₀ are associated with variations in the roughness geometry. The roughness measurements suggest that the estimated values of z₀ are consistent with the presence of irregular roughness structures that develop during snowfalls that mimic ballistic deposition processes.

Original language	English (US)
Pages (from-to)	21-34
Number of pages	14
Journal	Boundary-Layer Meteorology
Volume	141
Issue number	1
DOIs	https://doi.org/10.1007/s10546-011-9623-3
State	Published - Oct 2011

Bibliographical note

Funding Information:
Acknowledgements The study and wind-tunnel facility were partially funded by the Swiss National Science Foundation and by the Vontobel foundation (Benjamin Walter). Technical support from the SLF workshop is acknowledged. The authors wish to thank Frank Graf, Andy Clifton and Katherine Leonard from the WSL Institute for Snow and Avalanche Research SLF for many helpful discussions and Michael Raupach from CSIRO for kindly providing the data reported in Figs. 7 and 8.

Keywords

Aerodynamic roughness length
Hot-film anemometry
Rough-wall turbulent boundary layer
Snow
Surface roughness
Wind tunnel

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10.1007/s10546-011-9623-3

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title = "Aerodynamic Roughness Length of Fresh Snow",

abstract = "This study presents the results from a series of wind-tunnel experiments designed to investigate the aerodynamic roughness length z0 of fresh snow under no-drift conditions. A two-component hot-film anemometer was employed to obtain vertical profiles of velocity statistics in a zero pressure gradient turbulent boundary layer for flow over naturally deposited snow surfaces. The roughness of these snow surfaces was measured by means of digital photography to capture characteristic length scales that can be related to z0. Our results show that, under aerodynamically rough conditions, the mean value of the roughness length for fresh snow is 〈z0〉=0.24 mm with a standard deviation σ(z0) = 0.05 mm. In this study, we show that variations in z0 are associated with variations in the roughness geometry. The roughness measurements suggest that the estimated values of z0 are consistent with the presence of irregular roughness structures that develop during snowfalls that mimic ballistic deposition processes.",

keywords = "Aerodynamic roughness length, Hot-film anemometry, Rough-wall turbulent boundary layer, Snow, Surface roughness, Wind tunnel",

author = "Christof Gromke and Costantino Manes and Benjamin Walter and Michael Lehning and Michele Guala",

note = "Funding Information: Acknowledgements The study and wind-tunnel facility were partially funded by the Swiss National Science Foundation and by the Vontobel foundation (Benjamin Walter). Technical support from the SLF workshop is acknowledged. The authors wish to thank Frank Graf, Andy Clifton and Katherine Leonard from the WSL Institute for Snow and Avalanche Research SLF for many helpful discussions and Michael Raupach from CSIRO for kindly providing the data reported in Figs. 7 and 8.",

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doi = "10.1007/s10546-011-9623-3",

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AU - Manes, Costantino

AU - Walter, Benjamin

AU - Lehning, Michael

AU - Guala, Michele

N1 - Funding Information: Acknowledgements The study and wind-tunnel facility were partially funded by the Swiss National Science Foundation and by the Vontobel foundation (Benjamin Walter). Technical support from the SLF workshop is acknowledged. The authors wish to thank Frank Graf, Andy Clifton and Katherine Leonard from the WSL Institute for Snow and Avalanche Research SLF for many helpful discussions and Michael Raupach from CSIRO for kindly providing the data reported in Figs. 7 and 8.

PY - 2011/10

Y1 - 2011/10

N2 - This study presents the results from a series of wind-tunnel experiments designed to investigate the aerodynamic roughness length z0 of fresh snow under no-drift conditions. A two-component hot-film anemometer was employed to obtain vertical profiles of velocity statistics in a zero pressure gradient turbulent boundary layer for flow over naturally deposited snow surfaces. The roughness of these snow surfaces was measured by means of digital photography to capture characteristic length scales that can be related to z0. Our results show that, under aerodynamically rough conditions, the mean value of the roughness length for fresh snow is 〈z0〉=0.24 mm with a standard deviation σ(z0) = 0.05 mm. In this study, we show that variations in z0 are associated with variations in the roughness geometry. The roughness measurements suggest that the estimated values of z0 are consistent with the presence of irregular roughness structures that develop during snowfalls that mimic ballistic deposition processes.

AB - This study presents the results from a series of wind-tunnel experiments designed to investigate the aerodynamic roughness length z0 of fresh snow under no-drift conditions. A two-component hot-film anemometer was employed to obtain vertical profiles of velocity statistics in a zero pressure gradient turbulent boundary layer for flow over naturally deposited snow surfaces. The roughness of these snow surfaces was measured by means of digital photography to capture characteristic length scales that can be related to z0. Our results show that, under aerodynamically rough conditions, the mean value of the roughness length for fresh snow is 〈z0〉=0.24 mm with a standard deviation σ(z0) = 0.05 mm. In this study, we show that variations in z0 are associated with variations in the roughness geometry. The roughness measurements suggest that the estimated values of z0 are consistent with the presence of irregular roughness structures that develop during snowfalls that mimic ballistic deposition processes.

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KW - Surface roughness

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Aerodynamic Roughness Length of Fresh Snow

Abstract

Bibliographical note

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