scholarly journals Simulation of the specific surface area of snow using a one-dimensional physical snowpack model: implementation and evaluation for subarctic snow in Alaska

2010 ◽  
Vol 4 (1) ◽  
pp. 35-51 ◽  
Author(s):  
H.-W. Jacobi ◽  
F. Domine ◽  
W. R. Simpson ◽  
T. A. Douglas ◽  
M. Sturm
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Winter Season ◽  
Data Set ◽  
Thermal Budget ◽  
One Dimensional ◽  
Snow Model ◽  
Physics Model ◽  
Snow Physics

Abstract. The specific surface area (SSA) of the snow constitutes a powerful parameter to quantify the exchange of matter and energy between the snow and the atmosphere. However, currently no snow physics model can simulate the SSA. Therefore, two different types of empirical parameterizations of the specific surface area (SSA) of snow are implemented into the existing one-dimensional snow physics model CROCUS. The parameterizations are either based on diagnostic equations relating the SSA to parameters like snow type and density or on prognostic equations that describe the change of SSA depending on snow age, snowpack temperature, and the temperature gradient within the snowpack. Simulations with the upgraded CROCUS model were performed for a subarctic snowpack, for which an extensive data set including SSA measurements is available at Fairbanks, Alaska for the winter season 2003/2004. While a reasonable agreement between simulated and observed SSA values is obtained using both parameterizations, the model tends to overestimate the SSA. This overestimation is more pronounced using the diagnostic equations compared to the results of the prognostic equations. Parts of the SSA deviations using both parameterizations can be attributed to differences between simulated and observed snow heights, densities, and temperatures. Therefore, further sensitivity studies regarding the thermal budget of the snowpack were performed. They revealed that reducing the thermal conductivity of the snow or increasing the turbulent fluxes at the snow surfaces leads to a slight improvement of the simulated thermal budget of the snowpack compared to the observations. However, their impact on further simulated parameters like snow height and SSA remains small. Including additional physical processes in the snow model may have the potential to advance the simulations of the thermal budget of the snowpack and, thus, the SSA simulations.

scholarly journals Simulation of the specific surface area of snow using a one-dimensional physical snowpack model: implementation and evaluation for subarctic snow in Alaska

2009 ◽  
Vol 3 (3) ◽  
pp. 681-728 ◽  
Author(s):  
H. W. Jacobi ◽  
F. Domine ◽  
W. R. Simpson ◽  
T. A. Douglas ◽  
M. Sturm
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Winter Season ◽  
Data Set ◽  
Thermal Budget ◽  
One Dimensional ◽  
Snow Model ◽  
Physics Model ◽  
Snow Physics

Abstract. The specific surface area (SSA) of the snow constitutes a powerful parameter to quantify the exchange of matter and energy between the snow and the atmosphere. However, currently no snow physics model can simulate the SSA. Therefore, two different types of empirical parameterizations of the specific surface area (SSA) of snow are implemented into the existing one-dimensional snow physics model CROCUS. The parameterizations are either based on diagnostic equations relating the SSA to parameters like snow type and density or on prognostic equations that describe the change of SSA depending on snow age, snowpack temperature, and the temperature gradient within the snowpack. Simulations with the upgraded CROCUS model were performed for a subarctic snowpack, for which an extensive data set including SSA measurements is available at Fairbanks, Alaska for the winter season 2003/2004. While a reasonable agreement between simulated and observed SSA values is obtained using both parameterizations, the model tends to overestimate the SSA. This overestimation is more pronounced using the diagnostic equations compared to the results of the prognostic equations. Parts of the SSA deviations using both parameterizations can be attributed to differences between simulated and observed snow heights, densities, and temperatures. Therefore, further sensitivity studies regarding the thermal budget of the snowpack were performed. They revealed that reducing the heat conductivity of the snow or increasing the turbulent fluxes at the snow surfaces leads to a slight improvement of the simulated thermal budget of the snowpack compared to the observations. However, their impact on further simulated parameters like snow height and SSA remains small. Including additional physical processes in the snow model may have the potential to advance the simulations of the thermal budget of the snowpack and, thus, the SSA simulations.

scholarly journals Snow physics as relevant to snow photochemistry

2007 ◽  
Vol 7 (3) ◽  
pp. 5941-6036 ◽  
Author(s):  
F. Domine ◽  
M. Albert ◽  
T. Huthwelker ◽  
H.-W. Jacobi ◽  
A. A. Kokhanovsky ◽  
...  
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Quantitative Description ◽  
Field Measurements ◽  
Liquid Water Content ◽  
Reactive Gases ◽  
Snow Physics ◽  
Snow Photochemistry

Abstract. Snow on the ground is a complex multiphase photochemical reactor that dramatically modifies the chemical composition of the overlying atmosphere. A quantitative description of the emissions of reactive gases by snow requires the knowledge of snow physical properties. This overview details our current understanding of how those physical properties relevant to snow photochemistry vary during snow metamorphism. Properties discussed are density, specific surface area, optical properties, thermal conductivity, permeability and gas diffusivity. Inasmuch as possible, equations to parameterize these properties as a function of climatic variables are proposed, based on field measurements, laboratory experiments and theory. The potential of remote sensing methods to obtain information on some snow physical variables such as grain size, liquid water content and snow depth are discussed. The possibilities for and difficulties of building a snow photochemistry model by adapting current snow physics models are explored. Elaborate snow physics models already exist, and including variables of particular interest to snow photochemistry such as light fluxes and specific surface area appears possible. On the other hand, understanding the nature and location of reactive molecules in snow seems to be the greatest difficulty modelers will have to face for lack of experimental data, and progress on this aspect will require the detailed study of natural snow samples.

scholarly journals Efficient Sunlight-Induced Methylene Blue Removal over One-Dimensional Mesoporous Monoclinic BiVO4Nanorods

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Linrui Hou ◽  
Long Yang ◽  
Jiaoyang Li ◽  
Jie Tan ◽  
Changzhou Yuan
Keyword(s):  
Methylene Blue ◽  
Specific Surface ◽  
Band Gap ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mesoporous Structure ◽  
High Specific Surface Area ◽  
One Dimensional ◽  
Light Region ◽  
Degussa P25

Sunlight-driven mesoporous BiVO4nanorods with monoclinic structure have been successfully synthesizedviaa simple hydrothermal method. The as-prepared one-dimensional BiVO4nanorods exhibited high specific surface area due to their unique mesoporous structure. The mesoporous BiVO4nanorods possessed strong photoabsorption properties in the visible light region as well as the ultravisible region, and the band gap was estimated to beca.2.18 eV. The photocatalytic activities were evaluated by decolorization of methylene blue under sunlight irradiation. Photocatalytic tests demonstrated that the decolorization rate of as-prepared mesoporous BiVO4nanorods was even up to 98.8% in 180 min, much better than that prepared by solid-state reaction (23.1%) and the commercial TiO2(Degussa P25) (14.2%) under the same conditions, due to their higher specific surface area and appropriate band gap. Moreover, the unique BiVO4nanorods exhibit high stability after five photocatalytic degradation recycles.

scholarly journals Transition metal sulfides meet electrospinning: versatile synthesis, distinct properties and prospective applications

Nanoscale ◽  
2021 ◽  
Author(s):  
Wendong Zhu ◽  
Ya Cheng ◽  
Ce Wang ◽  
Nicola Pinna ◽  
Xiaofeng Lu
Keyword(s):  
Transition Metal ◽  
Mass Transport ◽  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Metal Sulfides ◽  
Large Specific Surface Area ◽  
One Dimensional ◽  
Significant Attention

One-dimensional (1D) electrospun nanomaterials have attracted significant attention due to their unique structures and outstanding chemical and physical properties such as large specific surface area, distinct electronic and mass transport,...

scholarly journals Snow physics as relevant to snow photochemistry

2008 ◽  
Vol 8 (2) ◽  
pp. 171-208 ◽  
Author(s):  
F. Domine ◽  
M. Albert ◽  
T. Huthwelker ◽  
H.-W. Jacobi ◽  
A. A. Kokhanovsky ◽  
...  
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Quantitative Description ◽  
Field Measurements ◽  
Liquid Water Content ◽  
Reactive Gases ◽  
Snow Physics ◽  
Snow Photochemistry

Abstract. Snow on the ground is a complex multiphase photochemical reactor that dramatically modifies the chemical composition of the overlying atmosphere. A quantitative description of the emissions of reactive gases by snow requires knowledge of snow physical properties. This overview details our current understanding of how those physical properties relevant to snow photochemistry vary during snow metamorphism. Properties discussed are density, specific surface area, thermal conductivity, permeability, gas diffusivity and optical properties. Inasmuch as possible, equations to parameterize these properties as functions of climatic variables are proposed, based on field measurements, laboratory experiments and theory. The potential of remote sensing methods to obtain information on some snow physical variables such as grain size, liquid water content and snow depth are discussed. The possibilities for and difficulties of building a snow photochemistry model by adapting current snow physics models are explored. Elaborate snow physics models already exist, and including variables of particular interest to snow photochemistry such as light fluxes and specific surface area appears possible. On the other hand, understanding the nature and location of reactive molecules in snow seems to be the greatest difficulty modelers will have to face for lack of experimental data, and progress on this aspect will require the detailed study of natural snow samples.

scholarly journals Intercomparison of retrieval algorithms for the specific surface area of snow from near-infrared satellite data in mountainous terrain, and comparison with the output of a semi-distributed snowpack model

2013 ◽  
Vol 7 (2) ◽  
pp. 741-761 ◽  
Author(s):  
A. Mary ◽  
M. Dumont ◽  
J.-P. Dedieu ◽  
Y. Durand ◽  
P. Sirguey ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Near Infrared ◽  
Winter Season ◽  
Added Value ◽  
Mountainous Terrain ◽  
Multiple Reflections ◽  
Topographic Correction ◽  
Wide Range

Abstract. This study compares different methods to retrieve the specific surface area (SSA) of snow from satellite radiance measurements in mountainous terrain. It aims at addressing the effect on the retrieval of topographic corrections of reflectance, namely slope and aspect of terrain, multiple reflections on neighbouring slopes and accounting (or not) for the anisotropy of snow reflectance. Using MODerate resolution Imaging Spectrometer (MODIS) data for six different clear sky scenes spanning a wide range of snow conditions during the winter season 2008–2009 over a domain of 46 × 50 km in the French Alps, we compared SSA retrievals with and without topographic correction, with a spherical or non-spherical snow reflectance model and, in spherical case, with or without anisotropy corrections. The retrieved SSA values were compared to field measurements and to the results of the detailed snowpack model Crocus, fed by driving data from the SAFRAN meteorological analysis. It was found that the difference in terms of surface SSA between retrieved values and SAFRAN-Crocus output was minimal when the topographic correction was taken into account, when using a retrieval method assuming disconnected spherical snow grains. In this case, the root mean square deviation was 9.4 m2 kg−1 and the mean difference was 0.1 m2 kg−1, based on 3170 pairs of observation and simulated values. The added-value of the anisotropy correction was not significant in our case, which may be explained by the presence of mixed pixels and surface roughness. MODIS retrieved data show SSA variations with elevation and aspect which are physically consistent and in good agreement with SAFRAN-Crocus outputs. The variability of the MODIS retrieved SSA within the topographic classes of the model was found to be relatively small (3.9 m2 kg−1). This indicates that semi-distributed snowpack simulations in mountainous terrain with a sufficiently large number of classes provides a representation of the snowpack variability consistent with the scale of MODIS 500 m pixels.

scholarly journals The growth of sublimation crystals and surface hoar on the Antarctic plateau

2013 ◽  
Vol 7 (6) ◽  
pp. 5971-5999
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
J. Savarino ◽  
M. Dumont ◽  
E. Brun
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Temperature Drop ◽  
Antarctic Plateau ◽  
Snow Crystal ◽  
Time Variations ◽  
Frost Flowers ◽  
Snow Model ◽  
The Antarctic

Abstract. On the Antarctic plateau, the budget of water vapor and energy is in part determined by precipitation, but these are so low that the dynamic of snow crystal growth and sublimation at the surface can be important factors. At Dome C (75° S, 123° E), we have frequently observed the growth of crystals on the snow surface under calm sunny weather. Here, we present the time variations of specific surface area and density of these crystals. Using the detailed snow model Crocus, we conclude that these crystals were very likely due to the nighttime formation of surface hoar crystals and to the daytime formation of sublimation crystals. These latter crystals form by processes similar to those involved in the formation of frost flowers on young sea ice. The formation of these crystals impact the albedo, mass and energy budget of the Antarctic plateau. In particular, the specific surface area variations of the surface layer can induce an instantaneous forcing of up to −10 W m−2 at noon, resulting in a surface temperature drop of 0.45 K.

scholarly journals Influence of stress, temperature and crystal morphology on isothermal densification and specific surface area decrease of new snow

2014 ◽  
Vol 8 (5) ◽  
pp. 1825-1838 ◽  
Author(s):  
S. Schleef ◽  
H. Löwe ◽  
M. Schneebeli
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Linear Relation ◽  
Crystal Habit ◽  
High Temporal Resolution ◽  
Densification Rate ◽  
Experimental Conditions ◽  
Data Set ◽  
Decrease Rate

Abstract. Laboratory-based, experimental data for the microstructural evolution of new snow are scarce, though applications would benefit from a quantitative characterization of the main influences. To this end, we have analyzed the metamorphism and concurrent densification of new snow under isothermal conditions by means of X-ray microtomography and compiled a comprehensive data set of 45 time series. In contrast to previous measurements on isothermal metamorphism on time scales of weeks to months, we analyzed the initial 24–48 h of snow evolution at a high temporal resolution of 3 hours. The data set comprised natural and laboratory-grown snow, and experimental conditions included systematic variations of overburden stress, temperature and crystal habit to address the main influences on specific surface area (SSA) decrease rate and densification rate in a snowpack. For all conditions, we found a linear relation between density and SSA, indicating that metamorphism has an immediate influence for the densification of new snow. The slope of the linear relation, however, depends on the other parameters which were analyzed individually to derive a best-fit parameterization for the SSA decrease rate and densification rate. In the investigated parameter range, we found that the initial value of the SSA constituted the main morphological influence on the SSA decrease rate. In turn, the SSA decrease rate constituted the main influence on the densification rate.

scholarly journals Influence of stress, temperature and crystal habit on isothermal densification and specific surface area decrease of new snow

2014 ◽  
Vol 8 (2) ◽  
pp. 1795-1829
Author(s):  
S. Schleef ◽  
H. Löwe ◽  
M. Schneebeli
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Crystal Habit ◽  
High Temporal Resolution ◽  
Time Behavior ◽  
Densification Rate ◽  
Experimental Conditions ◽  
Data Set ◽  
Decrease Rate

Abstract. Laboratory-based, experimental data for the microstructural evolution of new snow is scarce, though applications would benefit from a quantitative characterization of the main mechanism underlying the initial microstructural changes. To this end we have analyzed the metamorphism and concurrent densification of new snow under isothermal conditions by means of X-ray microtomography and compiled a comprehensive data set of 45 time series covering the practically relevant short time behavior within the first 24–48 h in high temporal resolution. The data set comprises natural and laboratory grown snow and experimental conditions include systematic variations of overburden stress, temperature and crystal habit to address the main influences on specific surface area (SSA) decrease rate and densification rate in a natural snowpack. For all conditions we find a linear increase of the density with the SSA, indicating that metamorphism has a key influence for the densification of new snow. Corroborated by the analysis of the individual influences of external conditions we derive a best-fit parametrization for the SSA decrease rate and the densification rate as required for applications.

Preparation, Characterization, and Photocatalytic Activity of LaMnO3 Nanorods-reduced Graphene Oxide Composite

2018 ◽  
Vol 14 (2) ◽  
pp. 117-126 ◽  
Author(s):  
Hao Huang ◽  
Mengru He ◽  
Liang Zhang ◽  
Benqian Lu ◽  
Jie Hu
Keyword(s):  
Graphene Oxide ◽  
Specific Surface ◽  
Reduced Graphene Oxide ◽  
Surface Area ◽  
Specific Surface Area ◽  
Perovskite Structure ◽  
Photocatalytic Performance ◽  
One Dimensional ◽  
Reduced Graphene ◽  
The One

Background: A new type of photocatalyst with a perovskite structure is recently utilized. The one-dimensional nanostructure of photocatalysts holds great charge mobility along the crystal longitudinal dimension and can hence provide the direct pathways of charge carriers. Graphene holds a superior electrical conductivity and high specific surface area. The aims of this paper are to make LaMnO3 nanorods disperse on the graphene surface. The synergistic effect between graphene and LaMnO3 nanorods enhances the photocatalytic performance. Method: LaMnO3 nanorods–graphene is fabricated using cetyltrimethyl ammonium bromide as template by a simple hydrothermal reaction followed by heat treatment. Results: XRD result indicates that the appropriate calcination temperature for the perovskite structure formation is 650°C. Electron microscopy reveals the LaMnO3 nanorods exhibit a good dispersion behavior on the surface of graphene and the specific surface area of LaMnO3 nanorods-graphene is higher than that of LaMnO3 nanorods. The activities of LaMnO3 nanorods–graphene and TiO2 are compared for degradation of Direct Green BE, the decolorizing rates are 99.93% and 79.45%, respectively. Conclusion: The photocatalytic results for Direct Green BE degradation showed that LaMnO3 nanorods– reduced graphene oxide exhibit a superior photocatalytic performance than that of LaMnO3 nanorods and TiO2 powders. The one-dimensional nanorod structure of LaMnO3 can provide a direct pathway for electronic transmission, and the increased aspect ratio is favorable for reducing the recombination probability of the electron and hole. Meanwhile, the photoelectron transport along the graphene sheets can promote the separation of the e−–h+ pairs.

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