Etude Experimentale De La Convection Thermique Dans La Neige

Brun, Élodie; Touvier, F.

doi:10.1051/jphyscol:1987136

Cited by 14 publications

(13 citation statements)

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“…Accurate measurements of k during experiments on thermal convection in snow confirmed this formula (Brun and Touvier, 1987). This coefficient is called effective since it includes heat fluxes due to vapor diffusion through the snow-pack and which may be formally considered as thermal conduction:…”

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confidence: 61%

An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting

et al. 1989

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ABSTRACT. A numerical model has been developed to simulate energy and mass evolution of snow cover at a given location , as a function of meteorological conditions: precipitation, air temperature, humidity, wind velocity, and incoming short-wave and long-wave radiation.This model, named CROCUS, was first tested on a well-instrumented field during a whole winter, showing its ability to simulate the important phenomena affecting the evolution of the snow layers: high temperature gradients, wetting, compaction, and melting-freezing cycles. A second test was conducted at two locations in the French network used for operational avalanche forecasting . Though the weather observations are made there only twice daily, the snow profiles calculated by the model were very close to those obtained once a week by a pit observation . CROCUS proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting .

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confidence: 61%

An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting

et al. 1989

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“…where ki is the ice conduction coefficient, P n and P w are snow and liquid water density. Accurate measurements of k during experiments on thermal convection in snow confirmed this formula (Brun and Touvier, 1987). This coefficient is called effective since it includes heat fluxes due to vapor diffusion through the snow-pack and which may be formally considered as thermal conduction:…”

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confidence: 75%

An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting

et al. 1989

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A numerical model has been developed to simulate energy and mass evolution of snow cover at a given location , as a function of meteorological conditions: precipitation, air temperature, humidity, wind velocity, and incoming short-wave and long-wave radiation.This model, named CROCUS, was first tested on a well-instrumented field during a whole winter, showing its ability to simulate the important phenomena affecting the evolution of the snow layers: high temperature gradients, wetting, compaction, and melting-freezing cycles. A second test was conducted at two locations in the French network used for operational avalanche forecasting . Though the weather observations are made there only twice daily, the snow profiles calculated by the model were very close to those obtained once a week by a pit observation . CROCUS proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting .

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“…Figure 10 would and that the surface temperature is constant through time. Racr for snow is usually assumed to be between 18 and 40, depending on whether the basal boundary is assumed to be subjected to a constant heat flux or a constant temperature [Lapwood, 1948;Nield, 1968;Akitaya, 1974;Palm and Tveitereid, 1979;Powers et al, 1985a, b;Brun and Touvier, 1987]. Heat flux varies by a factor of 10 at the base of the Fairbanks snow cover, but temperature remains nearly constant.…”

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confidence: 99%

“…Air convection in snow has been debated for more than 50 years [Bader et al, 1939;Akitaya, 1974;Trabant and Benson, 1972;Palm and Tveitereid, 1979;Powers et al, 1985a, b;Johnson et al, 1987;Brun and Touvier, 1987]. It is an important question, because convection may profoundly affect the snow cover.…”

Section: Introductionmentioning

confidence: 99%

“…Klever [1985] suggested that convection would be common in new snow but unlikely in snow composed of rounded grains. Brun and Touvier [1987] concluded that convection was unlikely, based on Rayleigh number calculations, nor were they able to induce convection in several types of snow samples in the laboratory, though none of the snow samples that they tested was of high permeability. It must be added, however, that theoreticians have generally held that convection would be common in snow lying on sloping ground [Bories and Combarnous, 1973;Combarnous and Bories, 1975;Powers et al, 1985a, b].…”

Section: Introductionmentioning

confidence: 99%

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Natural convection in the subarctic snow cover

Sturm¹,

Johnson²

1991

J. Geophys. Res.

124

114

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The purpose of this study was to determine if air convects in a natural snow cover. To detect convection, the temperature field in the subarctic snow cover in Fairbanks, Alaska, was measured hourly during three winters (1984)(1985)(1986)(1987) using an array of thermistors which were suspended on threads and allowed to be buried by snowfall. The results indicate that convection occurred sporadically in 1984-1985 and almost continuously in 1985-1986 and 1986-1987. The evidence was (1) simultaneous warming and cooling at different locations in a horizontal plane in the snow, and (2) horizontal temperature gradients of up to 16øC m -1 During the winter, warm and cold zones developed in the snow and remained relatively fixed in space. We interpret these zones to be the result of a diffuse plumelike convection pattern linked to spatial variations in the temperature of the snow-soil interface. Air flow was inferred to have been primarily horizontal near the base of the snow and vertical elsewhere, Calculated flow speeds were of the order of 0.2 mm s -l, with a maximum value of 2 mm s-1. The convective circulation was time-dependent, with perturbations such as high wind or rapid changes in air temperature triggering periods when horizontal temperature gradients were strongest, suggesting that these were also periods when the air flow was fastest. The coincidence of depth hoar crystals with horizontal c axes and the horizontal flow lines at the base of the snow suggests that convection may have affected crystal growth directions.

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Etude Experimentale De La Convection Thermique Dans La Neige

Cited by 14 publications

References 0 publications

An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting

An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting

An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting

Natural convection in the subarctic snow cover

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