scholarly journals Vertical profiles of the specific surface area of the snow at Dome C, Antarctica

2010 ◽  
Vol 4 (3) ◽  
pp. 1647-1708 ◽  
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
L. Arnaud ◽  
G. Picard ◽  
J. Savarino
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Austral Summer ◽  
Radiative Transfer Model ◽  
Integrating Sphere ◽  
Transfer Model ◽  
Vertical Profiles ◽  
Antarctic Plateau ◽  
The Antarctic

Abstract. The specific surface area (SSA) of snow determines in Part the albedo of snow surfaces and the capacity of the snow to adsorb chemical species and catalyze reactions. Despite these crucial roles, almost no value of snow SSA are available for the largest permanent snow expanse on Earth, the Antarctic. We have measured the first vertical profiles of snow SSA near Dome C (DC: 75°06´ S, 123°20´ E, 3233 m a.s.l.) on the Antarctic plateau, and at seven sites during the logistical traverse between Dome C and the French coastal base Dumont D'Urville (DDU: 66°40´ S, 140°01´ E) during the Austral summer 2008–2009. We used the DUFISSS system, which measures the IR reflectance of snow at 1310 nm with an integrating sphere. At DC, the mean SSA of the snow in the top 1 cm is 38 m2 kg−1, decreasing monotonically to 14 m2 kg−1 at a depth of 15 cm. Along the traverse, the snow SSA profile is similar to that at DC in the first 600 km from DC. Closer to DDU, the SSA of the top 5 cm is 23 m2 kg−1, decreasing to 19 m2 kg−1 at 50 cm depth. This is attributed to wind, which causes a rapid decrease of surface snow SSA, but forms hard windpacks whose SSA decrease more slowly with time. Since light-absorbing impurities are not concentrated enough to affect albedo, the vertical profiles of SSA and density were used to calculate the spectral albedo of the snow for several realistic illumination conditions, using the DISORT radiative transfer model. A preliminary comparison with MODIS data is presented for use in energy balance calculations and for comparison with other satellite retrievals. These calculated albedos are compared to the few existing measurements on the Antarctic plateau. The interest of postulating a submillimetric, high-SSA layer at the snow surface to explain measured albedos is discussed.

scholarly journals Vertical profile of the specific surface area and density of the snow at Dome C and on a transect to Dumont D'Urville, Antarctica – albedo calculations and comparison to remote sensing products

2011 ◽  
Vol 5 (3) ◽  
pp. 631-649 ◽  
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
L. Arnaud ◽  
G. Picard ◽  
J. Savarino
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Extensive Study ◽  
Radiative Transfer Model ◽  
Integrating Sphere ◽  
Transfer Model ◽  
Vertical Profiles ◽  
Modis Data ◽  
The Antarctic

Abstract. The specific surface area (SSA) of snow determines in part the albedo of snow surfaces and the capacity of the snow to adsorb chemical species and catalyze reactions. Despite these crucial roles, almost no value of snow SSA are available for the largest permanent snow expanse on Earth, the Antarctic. We report the first extensive study of vertical profiles of snow SSA near Dome C (DC: 75°06' S, 123°20' E, 3233 m a.s.l.) on the Antarctic plateau, and at seven sites during the logistical traverse between Dome C and the French coastal base Dumont D'Urville (DDU: 66°40' S, 140°01' E) during the Austral summer 2008–2009. We used the DUFISSS system, which measures the IR reflectance of snow at 1310 nm with an integrating sphere. At DC, the mean SSA of the snow in the top 1 cm is 38 m2 kg−1, decreasing monotonically to 14 m2 kg−1 at a depth of 50 cm. Along the traverse, the snow SSA profile is similar to that at DC in the first 600 km from DC. Closer to DDU, the SSA of the top 5 cm is 23 m2 kg−1, decreasing to 19 m2 kg−1 at 50 cm depth. This difference is attributed to wind, which causes a rapid decrease of surface snow SSA, but forms hard windpacks whose SSA decrease more slowly with time. Since light-absorbing impurities are not concentrated enough to affect albedo, the vertical profiles of SSA and density were used to calculate the spectral albedo of the snow for several realistic illumination conditions, using the DISORT radiative transfer model. A preliminary comparison with MODIS data is presented and our calculations and MODIS data show similar trends.

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 Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

2015 ◽  
Vol 9 (4) ◽  
pp. 4499-4538
Author(s):  
Q. Libois ◽  
G. Picard ◽  
L. Arnaud ◽  
M. Dumont ◽  
M. Lafaysse ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Summer Precipitation ◽  
Strong Wind ◽  
Near Surface ◽  
Antarctic Plateau ◽  
Annual Variability ◽  
Wind Events ◽  
The Antarctic

Abstract. On the Antarctic Plateau, snow specific surface area (SSA) close to the surface shows complex variations at daily to seasonal scales which affect the surface albedo and in turn the surface energy budget of the ice sheet. While snow metamorphism, precipitation and strong wind events are known to drive SSA variations, usually in opposite ways, their relative contributions remain unclear. Here, a comprehensive set of SSA observations at Dome C is analysed with respect to meteorological conditions to assess the respective roles of these factors. The results show an average two-to-three-fold SSA decrease from October to February in the topmost 10 cm, in response to the increase of air temperature and absorption of solar radiation in the snowpack during spring and summer. Surface SSA is also characterised by significant daily to weekly variations, due to the deposition of small crystals with SSA up to 100 m2 kg−1 onto the surface during snowfall and blowing snow events. To complement these field observations, the detailed snowpack model Crocus is used to simulate SSA, with the intent to further investigate the previously found correlation between inter-annual variability of summer SSA decrease and summer precipitation amount. To this end, Crocus parameterizations have been adapted to Dome C conditions, and the model was forced by ERA-Interim reanalysis. It successfully matches the observations at daily to seasonal time scales, except for few cases when snowfalls are not captured by the reanalysis. On the contrary, the inter-annual variability of summer SSA decrease is poorly simulated when compared to 14 years of microwave satellite data sensititve to the near surface SSA. A simulation with disabled summer precipitation confirms the weak influence in the model of the precipitation on metamorphism, with only 6 % enhancement. However we found that disabling strong wind events in the model is sufficient to reconciliate the simulations with the observations. This suggests that Crocus reproduces well the contributions of metamorphism and precipitation on surface SSA, but that snow compaction by the wind might be overestimated in the model.

scholarly journals Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

2015 ◽  
Vol 9 (6) ◽  
pp. 2383-2398 ◽  
Author(s):  
Q. Libois ◽  
G. Picard ◽  
L. Arnaud ◽  
M. Dumont ◽  
M. Lafaysse ◽  
...  
Keyword(s):  
Specific Surface ◽  
Interannual Variability ◽  
Surface Area ◽  
Specific Surface Area ◽  
Summer Precipitation ◽  
Strong Wind ◽  
Near Surface ◽  
Antarctic Plateau ◽  
Wind Events ◽  
The Antarctic

Abstract. On the Antarctic Plateau, snow specific surface area (SSA) close to the surface shows complex variations at daily to seasonal scales which affect the surface albedo and in turn the surface energy budget of the ice sheet. While snow metamorphism, precipitation and strong wind events are known to drive SSA variations, usually in opposite ways, their relative contributions remain unclear. Here, a comprehensive set of SSA observations at Dome C is analysed with respect to meteorological conditions to assess the respective roles of these factors. The results show an average 2-to-3-fold SSA decrease from October to February in the topmost 10 cm in response to the increase of air temperature and absorption of solar radiation in the snowpack during spring and summer. Surface SSA is also characterized by significant daily to weekly variations due to the deposition of small crystals with SSA up to 100 m2 kg−1 onto the surface during snowfall and blowing snow events. To complement these field observations, the detailed snowpack model Crocus is used to simulate SSA, with the intent to further investigate the previously found correlation between interannual variability of summer SSA decrease and summer precipitation amount. To this end, some Crocus parameterizations have been adapted to Dome C conditions, and the model was forced by ERA-Interim reanalysis. It successfully matches the observations at daily to seasonal timescales, except for the few cases when snowfalls are not captured by the reanalysis. On the contrary, the interannual variability of summer SSA decrease is poorly simulated when compared to 14 years of microwave satellite data sensitive to the near-surface SSA. A simulation with disabled summer precipitation confirms the weak influence in the model of the precipitation on metamorphism, with only 6 % enhancement. However, we found that disabling strong wind events in the model is sufficient to reconciliate the simulations with the observations. This suggests that Crocus reproduces well the contributions of metamorphism and precipitation on surface SSA, but snow compaction by the wind might be overestimated in the model.

scholarly journals Measuring the specific surface area of wet snow using 1310 nm reflectance

2014 ◽  
Vol 8 (4) ◽  
pp. 1139-1148 ◽  
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
M. Dumont
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Volume Ratio ◽  
Liquid Water Content ◽  
Optical Methods ◽  
Integrating Sphere ◽  
Wet Snow ◽  
The Difference

Abstract. The specific surface area (SSA) of snow can be used as an objective measurement of grain size and is therefore a central variable to describe snow physical properties such as albedo. Snow SSA can now be easily measured in the field using optical methods based on infrared reflectance. However, existing optical methods have only been validated for dry snow. Here we test the possibility to use the DUFISSS instrument, based on the measurement of the 1310 nm reflectance of snow with an integrating sphere, to measure the SSA of wet snow. We perform cold room experiments where we measure the SSA of a wet snow sample, freeze it and measure it again, to quantify the difference in reflectance between frozen and wet snow. We study snow samples in the SSA range 12–37 m2 kg−1 and in the mass liquid water content (LWC) range 5–32%. We conclude that the SSA of wet snow can be obtained from the measurement of its 1310 nm reflectance using three simple steps. In most cases, the SSA thus obtained is less than 10 {%} different from the value that would have been obtained if the sample had been considered dry, so that the three simple steps constitute a minor correction. We also run two optical models to interpret the results, but no model reproduces correctly the water–ice distribution in wet snow, so that their predictions of wet snow reflectance are imperfect. The correction on the determination of wet snow SSA using the DUFISSS instrument gives an overall uncertainty better than 11%, even if the LWC is unknown. If SSA is expressed as a surface to volume ratio (e.g., in mm−1), the uncertainty is then 13% because of additional uncertainties in the determination of the volume of ice and water when the LWC is unknown.

scholarly journals Impact of radiation penetration on Antarctic surface melt and subsurface snow temperatures in RACMO2.3p3

2021 ◽  
Author(s):  
Christiaan Timo van Dalum ◽  
Willem Jan van de Berg ◽  
Michiel Roland van den Broeke
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
Surface Mass ◽  
Surface Melt ◽  
The Antarctic ◽  
The Impact ◽  
Snow Temperature

Abstract. This study investigates the sensitivity of modeled surface melt and subsurface heating on the Antarctic ice sheet to a new spectral snow albedo and radiative transfer scheme in the Regional Atmospheric Climate Model (RACMO2), version 2.3p3 (Rp3). We tune Rp3 to observations by performing several sensitivity experiments and assess the impact on temperature and melt by changing one parameter at a time. When fully tuned, Rp3 compares well with in situ and remote sensing observations of surface mass and energy balance, melt, temperature, albedo and snow grain specific surface area. Furthermore, the introduction of subsurface heating in Rp3 significantly improves the snow temperature profile. Near surface snow temperature is especially sensitive to the prescribed fresh snow specific surface area and fresh dry snow metamorphism. These processes, together with the refreezing grain size and subsurface heating, are important for melt around the margins of the Antarctic ice sheet. Moreover, small changes in the albedo and the aforementioned processes can lead to an order of magnitude overestimation of melt, locally leading to runoff and a reduced surface mass balance.

scholarly journals Measurement of the specific surface area of snow using infrared reflectance in an integrating sphere at 1310 and 1550 nm

2009 ◽  
Vol 3 (2) ◽  
pp. 167-182 ◽  
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
C. S. Zender ◽  
G. Picard
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Integrating Sphere ◽  
Infrared Reflectance ◽  
Dual Frequency ◽  
Climatic Impact ◽  
Area Index ◽  
Alpine Regions ◽  
Few Data

Abstract. Even though the specific surface area (SSA) and the snow area index (SAI) of snow are crucial variables to determine the chemical and climatic impact of the snow cover, few data are available on the subject. We propose here a novel method to measure snow SSA and SAI. It is based on the measurement of the hemispherical infrared reflectance of snow samples using the DUFISSS instrument (DUal Frequency Integrating Sphere for Snow SSA measurement). DUFISSS uses the 1310 or 1550 nm radiation of laser diodes, an integrating sphere 15 cm in diameter, and InGaAs photodiodes. For SSA<60 m2 kg−1, we use the 1310 nm radiation, reflectance is between 15 and 50% and the accuracy of SSA determination is 10%. For SSA>60 m2 kg−1, snow is usually of low density (typically 30 to 100 kg m−3), resulting in insufficient optical depth and 1310 nm radiation reaches the bottom of the sample, causing artifacts. The 1550 nm radiation is therefore used for SSA>60 m2 kg−1. Reflectance is then in the range 5 to 12% and the accuracy on SSA is 12%. We propose empirical equations to determine SSA from reflectance at both wavelengths, with that for 1310 nm taking into account the snow density. DUFISSS has been used to measure the SSA of snow and the SAI of snowpacks in polar and Alpine regions.

scholarly journals New shortwave infrared albedo measurements for snow specific surface area retrieval

2012 ◽  
Vol 58 (211) ◽  
pp. 941-952 ◽  
Author(s):  
B. Montpetit ◽  
A. Royer ◽  
A. Langlois ◽  
P. Cliche ◽  
A. Roy ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Near Infrared ◽  
Infrared Camera ◽  
Optical Methods ◽  
Integrating Sphere ◽  
Snow Stratigraphy ◽  
Size Characterization ◽  
Shortwave Infrared

AbstractSnow grain-size characterization, its vertical and temporal evolution is a key parameter for the improvement and validation of snow and radiative transfer models (optical and microwave) as well as for remote-sensing retrieval methods. We describe two optical methods, one active and one passive shortwave infrared, for field determination of the specific surface area (SSA) of snow grains. We present a new shortwave infrared (SWIR) camera approach. This new method is compared with a SWIR laser- based system measuring snow albedo with an integrating sphere (InfraRed Integrating Sphere (IRIS)). Good accuracy (10%) and reproducibility in SSA measurements are obtained using the IRIS system on snow samples having densities greater than 200 kg m-3, validated against X-ray microtomography measurements. The SWIRcam approach shows improved sensitivity to snow SSA when compared to a near-infrared camera, giving a better contrast of the snow stratigraphy in a snow pit.

scholarly journals Rapid and accurate measurement of the specific surface area of snow using infrared reflectance at 1310 and 1550 nm

2009 ◽  
Vol 3 (1) ◽  
pp. 33-75 ◽  
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
C. S. Zender ◽  
G. Picard
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Atmospheric Chemistry ◽  
Integrating Sphere ◽  
Dual Frequency ◽  
Climatic Impact ◽  
Area Index ◽  
A Value ◽  
Few Data

Abstract. Even though the specific surface area (SSA) of snow is a crucial variable to determine the chemical and climatic impact of the snow cover, few data are available on snow SSA because current measurement methods are not simple to use in the field or do not have a sufficient accuracy. We propose here a novel determination method based on the measurement of the hemispherical reflectance of snow in the infrared using the DUFISSS instrument (DUal Frequency Integrating Sphere for Snow SSA measurement). DUFISSS uses 1310 and 1550 nm radiation provided by laser diodes, an integrating sphere 15 cm in diameter, and InGaAs photodiodes. For SSA<60 m2 kg−1, we use the 1310 nm radiation, reflectance is in the range 15 to 50% and the accuracy is 10%. For SSA>60 m2 kg−1, snow is usually of low to very low density (typically 30 to 100 kg m−3) and this produces artifacts caused by the e-folding length of light in snow being too long. We therefore use 1550 nm radiation for SSA>60 m2 kg−1. Reflectance is then in the range 5 to 12%, and the accuracy is 12%. No effect of crystal shape on reflectance was detected. We propose empirical equations to determine SSA from reflectance at both wavelengths, with that for 1310 nm taking into account the snow density. DUFISSS has been tested in the Alps to measure the snow area index (SAI) of the Alpine snowpack in a south facing area at 2100 m elevation. This was done by measuring the SSA, thickness and density of the seven main layers of the snowpack in just 30 min, and a value of 5350 was found, significantly greater than in Arctic and subarctic regions. DUFISSS can now be used to help study issues related to polar and Alpine atmospheric chemistry and climate.

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