scholarly journals Effect of unsteady wind on drifting snow: first investigations

2002 ◽  
Vol 2 (3/4) ◽  
pp. 129-136 ◽  
Author(s):  
J.-L. Michaux ◽  
F. Naaim-Bouvet ◽  
M. Naaim ◽  
M. Lehning ◽  
G. Guyomarc’h
Keyword(s):  
Wind Tunnel ◽  
Numerical Models ◽  
Wind Gust ◽  
Strong Wind ◽  
Blowing Snow ◽  
Wind Tunnel Experiments ◽  
Drifting Snow ◽  
In Situ Experiments

Abstract. Wind is not always a steady flow. It can oscillate, producing blasts. However, most of the current numerical models of drifting snow are constrained by one major assumption: forcing winds are steady and uniform. Moreover, very few studies have been done to verify this hypothesis, because of the lack of available instrumentation and measurement difficulties. Therefore, too little is known about the possible role of wind gust in drifting snow. In order to better understand the effect of unsteady winds, we have performed both experiments at the climatic wind tunnel at the CSTB (Centre Scientifique et Technique des Bâtiments) in Nantes, France, and in situ experiments on our experimental high-altitude site, at the Lac Blanc Pass. These experiments were carried out collaboratively with Cemagref (France), Météo-France, and the IFENA (Switzerland). Through the wind tunnel experiments, we found that drifting snow is in a state of permanent disequilibrium in the presence of fluctuating airflows. In addition, the in situ experiments show that the largest drifting snow episodes appear during periods of roughly constant strong wind, whereas a short but strong blast does not produce significant drifting snow.  Key words. Drifting snow, blowing snow, gust, blast, acoustic sensor

scholarly journals Development of saltation layer of drifting snow

2004 ◽  
Vol 38 ◽  
pp. 35-38 ◽  
Author(s):  
Takeshi Sato ◽  
Kenji Kosugi ◽  
Atsushi Sato
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Snow Cover ◽  
Friction Velocity ◽  
Transport Rate ◽  
Strong Wind ◽  
Wind Tunnel Experiments ◽  
Drifting Snow ◽  
Starting Point

AbstractThe saltation length of aeolian snow particles and a new parameter, the ejection factor, which expresses the degree of erosion due to drifting snow, were obtained as functions of friction velocity by means of wind-tunnel experiments for semi-hard snow cover. The saturated-snowdrift transport rate was also obtained experimentally as a function of friction velocity. Based on these characteristics and the parameter, the development of the saltation layer of drifting snow along the fetch was simulated under various conditions such as snow hardness, wind speed and snowfall intensity. The main results are as follows. The developing distance denoting the distance required for the saltation layer to attain saturation, X sat, is determined by saltation length, ejection factor and saturated-snowdrift transport rate, all of which depend on wind speed. It is also affected by the magnitude of snowdrift transport rate at the starting point and by the intensity of snowfall if it exists. The dependence of Xsat on wind speed is not simple in the case of semi-hard snow cover: Xsat increases with wind speed under weak to moderate wind conditions and then decreases under moderate to strong wind conditions. It is sensitive to snow hardness: it is about one order longer on hard snow cover than on semi-hard snow cover. Snowfall reduces not only the value of Xsat but also its dependence on snow hardness.

scholarly journals Snow Control Studies of Elevated Buildings in the Antarctic

1983 ◽  
Vol 4 ◽  
pp. 188-191
Author(s):  
Hiromi Mitsuhashi ◽  
Toshio Hannuki ◽  
Toshio Sato ◽  
Kou Kusunoki
Keyword(s):  
Wind Tunnel ◽  
Blowing Snow ◽  
Wind Tunnel Experiments ◽  
Syowa Station ◽  
Design Concepts ◽  
Drifting Snow ◽  
Scale Models ◽  
The Difference ◽  
Wind Profiles ◽  
The Antarctic

To elaborate design concepts of elevated buildings in an area of drifting snow, snow deposition and wind profiles around two buildings at Syowa station, Antarctica, were observed in 1978. To interpret the observed results in detail, wind-tunnel experiments on scale models were carried out. A wind-scooped snow deposit was formed behind the building and a sharp ridge was formed on the lee side. The highest point of the deposit was at a distance of 1 or 1.5 times the floor height (about 1.5 m) and the skirt of the snowdrift extended about 5 times the height of the roof. Wind profiles measured near one of the buildings (ionosphere hut) were expressed in terms of the logarithmic law. Two methods based on wind-tunnel experiments were used to estimate the development of snowdrifts around the building: one is to estimate the deposition from the difference in transport of blowing snow calculated from wind profiles and snowdrift flux profiles, the other is by deduction from the distribution of wind profiles. These experiments together with previous ones indicated that the optimum floor height was about 44Î of the height of the building.

scholarly journals Snow Control Studies of Elevated Buildings in the Antarctic

1983 ◽  
Vol 4 ◽  
pp. 188-191
Author(s):  
Hiromi Mitsuhashi ◽  
Toshio Hannuki ◽  
Toshio Sato ◽  
Kou Kusunoki
Keyword(s):  
Wind Tunnel ◽  
Blowing Snow ◽  
Wind Tunnel Experiments ◽  
Syowa Station ◽  
Design Concepts ◽  
Drifting Snow ◽  
Scale Models ◽  
The Difference ◽  
Wind Profiles ◽  
The Antarctic

To elaborate design concepts of elevated buildings in an area of drifting snow, snow deposition and wind profiles around two buildings at Syowa station, Antarctica, were observed in 1978. To interpret the observed results in detail, wind-tunnel experiments on scale models were carried out. A wind-scooped snow deposit was formed behind the building and a sharp ridge was formed on the lee side. The highest point of the deposit was at a distance of 1 or 1.5 times the floor height (about 1.5 m) and the skirt of the snowdrift extended about 5 times the height of the roof. Wind profiles measured near one of the buildings (ionosphere hut) were expressed in terms of the logarithmic law. Two methods based on wind-tunnel experiments were used to estimate the development of snowdrifts around the building: one is to estimate the deposition from the difference in transport of blowing snow calculated from wind profiles and snowdrift flux profiles, the other is by deduction from the distribution of wind profiles. These experiments together with previous ones indicated that the optimum floor height was about 44Î of the height of the building.

scholarly journals Advanced experimental approaches to marine water-column biogeochemical processes

2017 ◽  
Vol 75 (1) ◽  
pp. 30-42 ◽  
Author(s):  
Louis Legendre ◽  
Richard B Rivkin ◽  
Nianzhi Jiao
Keyword(s):  
Water Column ◽  
Numerical Models ◽  
Free Water ◽  
Sea Surface ◽  
Biogeochemical Processes ◽  
In Situ Experiments ◽  
Technological Developments ◽  
Approaches To Study ◽  
Experimental Approaches

Abstract This “Food for Thought” article examines the potential uses of several novel scientific and technological developments, which are currently available or being developed, to significantly advance or supplement existing experimental approaches to study water-column biogeochemical processes (WCB-processes). After examining the complementary roles of observation, experiments and numerical models to study WCB-processes, we focus on the main experimental approaches of free-water in situ experiments, and at-sea and on-land meso- and macrocosms. We identify some of the incompletely resolved aspects of marine WCB-processes, and explore advanced experimental approaches that could be used to reduce their uncertainties. We examine three such approaches: free-water experiments of lengthened duration using bioArgo floats and gliders, at-sea mesocosms deployed several 100s m below the sea-surface using new biogeochemical sensors, and 50 m-tall on-land macrocosms. These approaches could lead to significant progress in concepts related to marine WCB-processes.

scholarly journals Drifting-snow studies over an instrumented mountainous site: II. Measurements and numerical model at small scale

2001 ◽  
Vol 32 ◽  
pp. 175-181 ◽  
Author(s):  
Jean-Luc Michaux ◽  
Florence Naaim-Bouvet ◽  
Mohamed Naaim
Keyword(s):  
Wind Speed ◽  
Numerical Model ◽  
Small Scale ◽  
Wind Gust ◽  
Strong Wind ◽  
Experimental Site ◽  
In Situ Data ◽  
Drifting Snow ◽  
Mean Wind Speed ◽  
Gust Factors

AbstractThe Érosion torrentielle, neige et avalanche (Etna) unit of CEMAGREF and the Centre d’Etudes de la Neige of Météo-France have been working on snowdrift for 10 years. A numerical model was developed at CEMAGREF to simulate snowdrift (Naaim and others, 1998). To validate this model on in situ data, a high-altitude experimental site was developed, located at 2700 m a.s.l. at the Lac Blanc Pass near the Alpe d’Huez ski resort. It is a nearly flat area and faces winds primarily from north and south. After describing the experimental site, we present the processed data of winter 1998/99. First, we analyze the data from CEMAGREF’s acoustic snowdrift sensor. It is sensitive to snow depth and snow-particle type, so additional calibration is necessary. Nevertheless, it allowed us to study non- stationary aspects of drifting snow. An analysis of gust factors for wind and drifting snow indicates that strong wind-gust factors exist in the mountains, and that drifting snow is more important during a regular and strong wind episode than during high wind-gust periods. Therefore, the numerical model presented here uses only the recorded mean wind speed. The model, which attempts to reproduce several days of storm, takes into account the modification of input parameters (e.g wind speed) as a function of time. The comparison between numerical results and measurements for a given meteorological event shows good agreement.

scholarly journals The Role of Electron Microscopy in Materials Science

1982 ◽  
Vol 35 (6) ◽  
pp. 727 ◽  
Author(s):  
PB Hirsch
Keyword(s):  
Electron Microscopy ◽  
Materials Science ◽  
Optical Techniques ◽  
Bulk Properties ◽  
In Situ Experiments ◽  
Powerful Means ◽  
Appropriate Scale ◽  
Powerful Electron

The properties of the materials in a component or a device depend on structure and composition often on a scale of 10-10 to 10-6 m. Electron microscopy and microanalytical techniques provide a powerful means for determining the structure and composition on the appropriate scale, lead to an understanding of basic mechanisms, and by correlation or in situ experiments to explanations of bulk properties. Examples are given of the application of a variety of powerful electron optical techniques to a number of materials problems.

scholarly journals The trophic biology of the holothurian <i>Molpadia musculus</i>: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon

2010 ◽  
Vol 7 (8) ◽  
pp. 2419-2432 ◽  
Author(s):  
T. Amaro ◽  
S. Bianchelli ◽  
D. S. M. Billett ◽  
M. R. Cunha ◽  
A. Pusceddu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ecosystem Functioning ◽  
Submarine Canyon ◽  
Gut Contents ◽  
Digestion Rate ◽  
In Situ Experiments ◽  
Total Digestion ◽  
Organic Matter Cycling

Abstract. Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m−2 d−1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

scholarly journals In Situ Experiments To Reveal the Role of Surface Feature Sidewalls in the Cassie–Wenzel Transition

Langmuir ◽  
2014 ◽  
Vol 30 (50) ◽  
pp. 15162-15170 ◽  
Author(s):  
René Hensel ◽  
Andreas Finn ◽  
Ralf Helbig ◽  
Sebastian Killge ◽  
Hans-Georg Braun ◽  
...  
Keyword(s):  
Surface Feature ◽  
In Situ Experiments

scholarly journals Wind-Tunnel Experiments on Blowing Snow

1985 ◽  
Vol 6 ◽  
pp. 63-67 ◽  
Author(s):  
N. Maeno ◽  
R. Naruse ◽  
K. Nishimura ◽  
I. Takei ◽  
T. Ebinuma ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Pressure Gradient ◽  
Blowing Snow ◽  
Wind Tunnel Experiments ◽  
Complex Dynamic ◽  
Turbulent Diffusion Coefficient ◽  
Wide Range ◽  
The Mean ◽  
Cold Wind ◽  
Snow Drifting

Blowing snow was produced artificially in a cold wind-tunnel, and various measurements were conducted including particle diameters, concentrations, saltation lengths heat transport and electric charge. The mean diameter of blowing snow particles decreased only slightly with increasing height; in the saltation layer, standard deviation was large and velocities were scattered in a wide range, suggesting the complex dynamic process on taking-off. The mean saltation length ranged from a few cm to 40 cm increasing with wind velocity.When wind blew without snow drifting, the static air pressure on the snow surface was smaller at higher levels, the vertical pressure gradient being negative. The pressure gradient became positive when blowing snow was initiated eg +9.6 Pa/m at 11.2 m/s and -8.3 °C. The magnitude of à downward force acting on a saltating snow partice caused by the pressure gradient was not large enough to explain the downward acceleration found from photographic analyses of particle trajectories.Blowing snow particles were charged negatively the magnitude of charge increased with lowering temperature. Increase in vertical heat transfer was found in blowing snow by measuring the temperature of the air at various levels; the increase is reflected on that in the apparent turbulent diffusion coefficient.

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