Development and calibration of an automatic spectral albedometer to estimate near-surface snow SSA time series

Picard, Ghislain; Libois, Quentin; Arnaud, Laurent; Verin, Gauthier; Dumont, Marie

doi:10.5194/tc-10-1297-2016

Cited by 71 publications

(140 citation statements)

References 65 publications

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“…In addition to the instrumental errors, the surface slope at the footprint scale may influence the retrieval results. Using data from Picard et al (2016), Dumont et al (2017) found variations of the surface slope caused by wind drift at Dome C of ±2 • . They estimated a resulting uncertainty of 10 % in retrieved SSA due to these variations of the surface slope.…”

Section: Retrieval Of Optical Snow Grain Size From Spectral Albedo Mementioning

confidence: 99%

“…Picard et al (2016) estimated that a hypothetical change in global surface albedo of 1 % would offset a difference in reflected energy comparable to the globally averaged radiative forcing of 1.82 W m −2 caused by the increase in CO 2 concentration since the preindustrial time (Myhre et al, 2013). This change in global surface albedo could be caused either by a variation in snow and sea ice cover or by a change of the snow albedo itself.…”

Section: Introductionmentioning

confidence: 99%

“…They measured a decrease in reflectance at 1310 nm wavelength by 45 % with increasing grain size from 290 to 1175 µm. Libois et al (2015) and Picard et al (2016) retrieved a 3-year time series of specific surface area (SSA) from spectral albedo measurements at Dome C (75 • 6 S, 123 • 0 E), Antarctica, which emphasized the dynamical evolution of near-surface SSA by displaying a 3-fold decrease every summer in response to the increase of air temperature. A detailed comparison of this dataset with snow model simulations and a geophysical interpretation are presented by Libois et al (2015).…”

Section: Introductionmentioning

confidence: 99%

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Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

et al. 2017

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Abstract. The optical-equivalent snow grain size affects the reflectivity of snow surfaces and, thus, the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA), from which the optical snow grain size is derived, was observed for a 2-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of ground-based spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS) and airborne observations with the Spectral Modular Airborne Radiation measurement sysTem (SMART). The snow grain size and pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified in order to reduce the impact of the solar zenith angle on the retrieval results and to cover measurements in overcast conditions. Spectral ratios of surface albedo at 1280 and 1100 nm wavelength were used to reduce the retrieval uncertainty. The retrieval was applied to the ground-based and airborne observations and validated against optical in situ observations of SSA utilizing an IceCube device. The SSA retrieved from CORAS observations varied between 27 and 89 m 2 kg −1 . Snowfall events caused distinct relative maxima of the SSA which were followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of freshly fallen ice crystals. The ability of the modified algorithm to include measurements in overcast conditions improved the data coverage, in particular at times when precipitation events occurred and the SSA changed quickly. SSA retrieved from measurements with CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved from the airborne SMART data slightly underestimated the ground-based results.

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Section: Retrieval Of Optical Snow Grain Size From Spectral Albedo Mementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

et al. 2017

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“…During the summer 2013/14, regular sampling of surface (0 to 3 cm) and sub-surface (3 to 6 cm) snow were carried out at Dome C. Once a day, two samples of snow at each level were taken along with specific surface area (SSA) measurements to 25 evaluate the size of the grains and therefore, how much metamorphism has taken place (Picard et al, 2016b). These data are presented in Fig.…”

Section: Surface and Sub-surface Snow Isotopic Exchangesmentioning

confidence: 99%

Archival processes of the water stable isotope signal in East Antarctic ice cores

Casado¹,

Landais²,

Picard³

et al. 2017

Preprint

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Abstract. The oldest ice core records are obtained from the East Antarctic plateau. Water isotopes records are key to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all the processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in Rayleigh distillation and isotope enabled climate models. However, a quantitative understanding of processes potentially altering the snow isotopic composition after the deposition is still missing. 5In low accumulation sites, such as those found in Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretation of isotopic composition.Here, we combine observations of isotopic composition in the vapour, the precipitation, the surface snow and the buried snow from Dome C, a deep ice core site on the East Antarctic Plateau. At the seasonal scale, we suggest a significant impact of 10 metamorphism on surface snow isotopic signal compared to the initial precipitation signal. Particularly, in summer, exchanges of water molecules between vapour and snow are driven by the sublimation/condensation cycles at the diurnal scale. Using highly resolved isotopic composition profiles from pits in five Antarctic sites, we identify common patterns, despite different accumulation rates, which cannot be attributed to the seasonal variability of precipitation. Altogether, the difference in the signals observed in the precipitation, surface snow and buried snow isotopic composition constitute evidences of post-deposition 15 processes affecting ice core records in low accumulation areas. 1The Cryosphere Discuss., https://doi

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“…There are no measurements of SSA recorded during 2009-2010 for skin layer snow. The SSA and effective grain radius in this study are estimated based on observations at Dome C from 2012 to 2015 by Picard et al (2016) as well as the annual temperature variation, as shown in Fig. B4.…”

Section: Other Model Inputsmentioning

confidence: 99%

Modelling the physical multiphase interactions of HNO<sub>3</sub> between snow and air on the Antarctic Plateau (Dome C) and coast (Halley)

2018

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Abstract. Emissions of nitrogen oxide (NO x = NO + NO 2 ) from the photolysis of nitrate (NO − 3 ) in snow affect the oxidising capacity of the lower troposphere especially in remote regions of high latitudes with little pollution. Current air-snow exchange models are limited by poor understanding of processes and often require unphysical tuning parameters. Here, two multiphase models were developed from physically based parameterisations to describe the interaction of nitrate between the surface layer of the snowpack and the overlying atmosphere. The first model is similar to previous approaches and assumes that below a threshold temperature, T o , the air-snow grain interface is pure ice and above T o a disordered interface (DI) emerges covering the entire grain surface. The second model assumes that air-ice interactions dominate over all temperatures below melting of ice and that any liquid present above the eutectic temperature is concentrated in micropockets. The models are used to predict the nitrate in surface snow constrained by year-round observations of mixing ratios of nitric acid in air at a cold site on the Antarctic Plateau (Dome C; 75 • 06 S, 123 • 33 E; 3233 m a.s.l.) and at a relatively warm site on the Antarctic coast (Halley; 75 • 35 S, 26 • 39 E; 35 m a.s.l). The first model agrees reasonably well with observations at Dome C (C v (RMSE) = 1.34) but performs poorly at Halley (C v (RMSE) = 89.28) while the second model reproduces with good agreement observations at both sites (C v (RMSE) = 0.84 at both sites). It is therefore suggested that in winter air-snow interactions of nitrate are determined by non-equilibrium surface adsorption and cocondensation on ice coupled with solid-state diffusion inside the grain, similar to Bock et al. (2016). In summer, however, the air-snow exchange of nitrate is mainly driven by solvation into liquid micropockets following Henry's law with contributions to total surface snow NO − 3 concentrations of 75 and 80 % at Dome C and Halley, respectively. It is also found that the liquid volume of the snow grain and airmicropocket partitioning of HNO 3 are sensitive to both the total solute concentration of mineral ions within the snow and pH of the snow. The second model provides an alternative method to predict nitrate concentration in the surface snow layer which is applicable over the entire range of environmental conditions typical for Antarctica and forms a basis for a future full 1-D snowpack model as well as parameterisations in regional or global atmospheric chemistry models.

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Development and calibration of an automatic spectral albedometer to estimate near-surface snow SSA time series

Cited by 71 publications

References 65 publications

Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

Archival processes of the water stable isotope signal in East Antarctic ice cores

Modelling the physical multiphase interactions of HNO<sub>3</sub> between snow and air on the Antarctic Plateau (Dome C) and coast (Halley)

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Development and calibration of an automatic spectral albedometer to estimate near-surface snow SSA time series

Cited by 71 publications

References 65 publications

Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

Archival processes of the water stable isotope signal in East Antarctic ice cores

Modelling the physical multiphase interactions of HNO&lt;sub&gt;3&lt;/sub&gt; between snow and air on the Antarctic Plateau (Dome C) and coast (Halley)

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Modelling the physical multiphase interactions of HNO<sub>3</sub> between snow and air on the Antarctic Plateau (Dome C) and coast (Halley)