ROLE OF WATER LAYER AT AN ICE SURFACE IN THE KINETIC PROCESSES OF GROWTH OF ICE CRYSTALS - GROWTH OF SNOW CRYSTALS AND FROST HEAVING

1987 ◽  
Vol 48 (C1) ◽  
pp. C1-487-C1-493 ◽  
Author(s):  
T. KURODA
Keyword(s):  
Water Layer ◽  
Ice Crystals ◽  
Frost Heaving ◽  
Ice Surface ◽  
Kinetic Processes ◽  
Snow Crystals

scholarly journals The Possible Importance of Electrical Forces in the Development of Snow Cornices

1970 ◽  
Vol 9 (57) ◽  
pp. 375-384 ◽  
Author(s):  
J. Latham ◽  
J. Montagne
Keyword(s):  
Ice Crystals ◽  
Western Montana ◽  
Ice Surface ◽  
Granular Crystals ◽  
Vertical Electric Field ◽  
Wind Velocities ◽  
Pressure Melting ◽  
Snow Crystals ◽  
Frictional Melting ◽  
Limiting Values

Measurements were made of the vertical electric field Strength around snow cornices on Bridger Ridge (2 590 m a.s.l.) in the Bridger Range, South-western Montana. The fields were considerably enhanced, owing to the exposed position of the cornices, but were nevertheless appreciably lower than those shown by Latham and Saunders (1970[b]) to be necessary in order to provide significant additional bonding when ice crystals collide with an ice surface. However, measurements made on Bridger Ridge and neighbouring Bangtail Ridge showed that the charges carried on snow crystals saltating over the surface of cornices were close to their limiting values.Rough calculations indicated that pressure melting is unlikely to be of importance in the development of snow cornices formed from granular crystals, that frictional melting is probably significant only at fairly low temperatures and moderately high wind velocities, and that strong electrostatic forces between highly charged snow crystals saltating over the surface of a cornice may be sufficient to provide bonding where the crystal velocities are comparatively low.

scholarly journals The Possible Importance of Electrical Forces in the Development of Snow Cornices

1970 ◽  
Vol 9 (57) ◽  
pp. 375-384 ◽  
Author(s):  
J. Latham ◽  
J. Montagne
Keyword(s):  
Ice Crystals ◽  
Western Montana ◽  
Ice Surface ◽  
Granular Crystals ◽  
Vertical Electric Field ◽  
Wind Velocities ◽  
Pressure Melting ◽  
Snow Crystals ◽  
Frictional Melting ◽  
Limiting Values

Measurements were made of the vertical electric field Strength around snow cornices on Bridger Ridge (2 590 m a.s.l.) in the Bridger Range, South-western Montana. The fields were considerably enhanced, owing to the exposed position of the cornices, but were nevertheless appreciably lower than those shown by Latham and Saunders (1970[b]) to be necessary in order to provide significant additional bonding when ice crystals collide with an ice surface. However, measurements made on Bridger Ridge and neighbouring Bangtail Ridge showed that the charges carried on snow crystals saltating over the surface of cornices were close to their limiting values.Rough calculations indicated that pressure melting is unlikely to be of importance in the development of snow cornices formed from granular crystals, that frictional melting is probably significant only at fairly low temperatures and moderately high wind velocities, and that strong electrostatic forces between highly charged snow crystals saltating over the surface of a cornice may be sufficient to provide bonding where the crystal velocities are comparatively low.

Temperature Gradient in the Unfrozen Liquid Layer for Multiphase Energy Balance With Incoming Droplets

2003 ◽  
Vol 125 (1) ◽  
pp. 186-189 ◽  
Author(s):  
G. F. Naterer
Keyword(s):  
Energy Balance ◽  
Water Layer ◽  
Surface Heat ◽  
Unfrozen Water ◽  
Temperature Variations ◽  
Proper Role ◽  
Ice Surface ◽  
Water Layers ◽  
Phase Change Heat Transfer

Phase change heat transfer with impinging supercooled droplets on an ice surface is examined. Partial solidification of incoming droplets leads to an unfrozen water layer above the ice. The significance of temperature variations within the water layer is considered. The multiphase energy balance is shown to approach the measured rate of ice growth when the surface heat input is lowered sufficiently. This asymptotic behavior is essential for establishing the proper role of heat conduction in the solid and liquid (unfrozen water) layers. Predicted results are successfully validated by comparisons with experimental data involving ice buildup on heated circular conductors.

scholarly journals The role of radiolysis in the modelling of C2H4O2 isomers and dimethyl ether in cold dark clouds

2020 ◽  
Vol 500 (3) ◽  
pp. 3414-3424
Author(s):  
Alec Paulive ◽  
Christopher N Shingledecker ◽  
Eric Herbst
Keyword(s):  
Gas Phase ◽  
Dimethyl Ether ◽  
Recent Observation ◽  
Cosmic Ray ◽  
Thermal Method ◽  
Dark Clouds ◽  
Ice Surface ◽  
Dust Grain ◽  
Complex Organic

ABSTRACT Complex organic molecules (COMs) have been detected in a variety of interstellar sources. The abundances of these COMs in warming sources can be explained by syntheses linked to increasing temperatures and densities, allowing quasi-thermal chemical reactions to occur rapidly enough to produce observable amounts of COMs, both in the gas phase, and upon dust grain ice mantles. The COMs produced on grains then become gaseous as the temperature increases sufficiently to allow their thermal desorption. The recent observation of gaseous COMs in cold sources has not been fully explained by these gas-phase and dust grain production routes. Radiolysis chemistry is a possible non-thermal method of producing COMs in cold dark clouds. This new method greatly increases the modelled abundance of selected COMs upon the ice surface and within the ice mantle due to excitation and ionization events from cosmic ray bombardment. We examine the effect of radiolysis on three C2H4O2 isomers – methyl formate (HCOOCH3), glycolaldehyde (HCOCH2OH), and acetic acid (CH3COOH) – and a chemically similar molecule, dimethyl ether (CH3OCH3), in cold dark clouds. We then compare our modelled gaseous abundances with observed abundances in TMC-1, L1689B, and B1-b.

scholarly journals Temporal and Spatial Coexistence of Archaeal and BacterialamoAGenes and Gene Transcripts in Lake Lucerne

Archaea ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Elisabeth W. Vissers ◽  
Flavio S. Anselmetti ◽  
Paul L. E. Bodelier ◽  
Gerard Muyzer ◽  
Christa Schleper ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Water Layer ◽  
Distribution Patterns ◽  
Freshwater Ecosystems ◽  
Ammonia Oxidizers ◽  
Lake Lucerne ◽  
Ammonia Oxidizing Archaea ◽  
Gene Transcripts ◽  
Temporal And Spatial

Despite their crucial role in the nitrogen cycle, freshwater ecosystems are relatively rarely studied for active ammonia oxidizers (AO). This study of Lake Lucerne determined the abundance of bothamoAgenes and gene transcripts of ammonia-oxidizing archaea (AOA) and bacteria (AOB) over a period of 16 months, shedding more light on the role of both AO in a deep, alpine lake environment. At the surface, at 42 m water depth, and in the water layer immediately above the sediment, AOA generally outnumbered AOB. However, in the surface water during summer stratification, when both AO were low in abundance, AOB were more numerous than AOA. Temporal distribution patterns of AOA and AOB were comparable. Higher abundances ofamoAgene transcripts were observed at the onset and end of summer stratification. In summer, archaealamoAgenes and transcripts correlated negatively with temperature and conductivity. Concentrations of ammonium and oxygen did not vary enough to explain theamoAgene and transcript dynamics. The observed herbivorous zooplankton may have caused a hidden flux of mineralized ammonium and a change in abundance of genes and transcripts. At the surface, AO might have been repressed during summer stratification due to nutrient limitation caused by active phytoplankton.

scholarly journals Oxycline oscillations induced by internal waves in deep Lake Iseo

2018 ◽  
Author(s):  
Giulia Valerio ◽  
Marco Pilotti ◽  
Maximilian Peter Lau ◽  
Michael Hupfer
Keyword(s):  
Internal Waves ◽  
Water Layer ◽  
Sediment Surface ◽  
Chemical Gradient ◽  
Deep Lakes ◽  
Deep Lake ◽  
Deep Waters ◽  
Basin Scale ◽  
First Time

Abstract. Lake Iseo is undergoing a dramatic de-oxygenation of the hypolimnion, representing an emblematic example among the deep lakes of the prealpine area that are, to a different extent, suffering from reduced deep water mixing. In the anoxic deep waters, the release and accumulation of reduced substances and phosphorus from the sediments is a major concern. Since the hydrodynamics of this lake was shown to be dominated by internal waves, in this study we investigate for the first time the role of these oscillatory motions on the vertical fluctuations of the oxycline, currently situated at a depth of around 95 m, where a permanent chemocline inhibits deep mixing by convection. Temperature and dissolved oxygen data measured at moored stations show large and periodic oscillations of the oxycline, with amplitude up to 20 m and periods ranging from 1 to 4 days. A deep dynamics characterized by larger amplitudes at lower frequencies is shown to be favoured by the excitation of second vertical modes in strongly thermally stratified periods and of first vertical modes in weakly thermally stratified periods, when the deep chemical gradient can support baroclinicity anyhow. These basin-scale internal waves cause in the water layer between 85 and 105 m depth a fluctuation of the oxygen concentration between 0 and 3 mg L−1 that, due to the bathymetry of the lake, changes the redox condition at the sediment surface. This forcing, involving about 3 % of the lake's sediment area, can have major implications for the biogeochemical processes at the sediment water interface and for the internal matter cycle.

scholarly journals Falling Mixed-Phase Ice Virga and their Liquid Parent Cloud Layers as Observed by Ground-Based Lidars

2020 ◽  
Vol 12 (13) ◽  
pp. 2094
Author(s):  
Chong Cheng ◽  
Fan Yi
Keyword(s):  
Local Maximum ◽  
Water Layer ◽  
Supercooled Liquid ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Cloud Base ◽  
Depolarization Ratio ◽  
Ice Crystal ◽  
Liquid Drops ◽  
The Mean

Falling mixed-phase virga from a thin supercooled liquid layer cloud base were observed on 20 occasions at altitudes of 2.3–9.4 km with ground-based lidars at Wuhan (30.5 °N, 114.4 °E), China. Polarization lidar profile (3.75-m) analysis reveals some ubiquitous features of both falling mixed-phase virga and their liquid parent cloud layers. Each liquid parent cloud had a well-defined base height where the backscatter ratio R was ~7.0 and the R profile had a clear inflection point. At an altitude of ~34 m above the base height, the depolarization ratio reached its minimum value (~0.04), indicating a liquid-only level therein. The thin parent cloud layers tended to form on the top of a broad preexisting aerosol/liquid water layer. The falling virga below the base height showed firstly a significant depolarization ratio increase, suggesting that most supercooled liquid drops in the virga were rapidly frozen into ice crystals (via contact freezing). After reaching a local maximum value of the depolarization ratio, both the values of the backscatter ratio and depolarization ratio for the virga exhibited an overall decrease with decreasing height, indicating sublimated ice crystals. The diameters of the ice crystals in the virga were estimated based on an ice particle sublimation model along with the lidar and radiosonde observations. It was found that the ice crystal particles in these virga cases tended to have smaller mean diameters and narrower size distributions with increasing altitude. The mean diameter value is 350 ± 111 µm at altitudes of 4–8.5 km.

Morphological Instability of Polyhedral Ice Crystals Growing in Air at Low Temperature

1985 ◽  
Vol 6 ◽  
pp. 222-224 ◽  
Author(s):  
T. Gonda ◽  
H. Gomi
Keyword(s):  
Low Temperature ◽  
Growth Rates ◽  
Crystal Size ◽  
Air Pressure ◽  
Experimental Results ◽  
Ice Crystals ◽  
Polar Regions ◽  
Morphological Instability ◽  
Skeletal Structures ◽  
Snow Crystals

The morphology of snow crystals growing at a low temperature has been experimentally studied. The habit and the morphological instability of the crystals vary remarkably with air pressure. In addition, the morphological instability of the crystals depends not only on air pressure but also on supersaturation, crystal size, the ratio of growth rates and the ratio of axial lengths. It is supposed from the experimental results that long prisms with small skeletal structures forming at low supersaturation are precipitating in polar regions.

The Role of Dissolved CH4 in Soil Solution in the CH4 Emission from Water-Saving Irrigated Rice Fields

2011 ◽  
Vol 148-149 ◽  
pp. 977-982
Author(s):  
Dao Xi Li
Keyword(s):  
Soil Solution ◽  
Early Stage ◽  
Dominant Role ◽  
Water Layer ◽  
Water Saving ◽  
Rice Fields ◽  
Chromatography Method ◽  
Soil Layers ◽  
Soil Solutions

To examine how the dissolved CH4 in soil solution would affect the CH4 emission from rice field, fluxes of CH4 emission were measured by using a manually closed static chamber-gas chromatography method, and the dissolved CH4 in soil solution was obtained through shaking soil solutions, which were extracted from different paddy soil layers by a soil solution sampler with suction and pressure. The results show that the CH4 fluxes from rice fields and the concentration of dissolved CH4 in soil solution are both reduced significantly under the water-saving irrigation as compared to the traditional flooded irrigation. Under the water-saving irrigation, naturally receding water-layer during the early stage leads to an earlier peak of CH4 flux, but dramatically reduces the concentration of dissolved CH4 in soil solution. The maximum concentration is shifted to about 20-cm depth soil layers, and the relationship between CH4 emissions and dissolved CH4 in soil solution can be estimated using an exponential function of dissolved CH4 in soil solution at the depth of about 20 cm (R2＝0.89, p4 in soil solution plays a more dominant role in CH4 emission under the water-saving irrigation than that under continuously flooded irrigation.

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