Rate of Evolution of the Specific Surface Area of Surface Snow Layers
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- 作者：Axel Cabanes ; Loï ; c Legagneux ; and Florent Dominé
- 刊名：Environmental Science & Technology
- 出版年：2003
- 出版时间：February 15, 2003
- 年：2003
- 卷：37
- 期：4
- 页码：661 - 666
- 全文大小：126K
- 年卷期：v.37,no.4(February 15, 2003)
- ISSN：1520-5851
文摘
The snowpack can impact atmospheric chemistry byexchanging adsorbed or dissolved gases with the atmosphere.Modeling this impact requires the knowledge of thespecific surface area (SSA) of snow and its variationswith time. We have therefore measured the evolution ofthe SSA of eight recent surface snow layers in the Arcticand the French Alps, using CH4 adsorption at liquidnitrogen temperature (77 K). The SSA of fresh snow layerswas found to decrease with time, from initial values inthe range 613-1540 cm2/g to values as low as 257 cm2/gafter 6 days. This is explained by snow metamorphism, whichcauses modifications in crystal shapes, here essentiallycrystal rounding and the disappearance of microstructures.A parametrization of the rate of SSA decrease is proposed.We fit the SSA decrease to an exponential law andfind that the time constant 
exp (day-1) depends ontemperature according to exp = 76.6 exp (-1708/T), withT in kelvin. Our parametrization predicts that the SSA ofa snow layer evolving at - 40 
C will decrease by a factorof 2 after 14 days, while a similar decrease at -1 Cwill only require 5 days. Wind was found to increase therate of SSA decrease, but insufficient data did not allow aparametrization of this effect.
exp (day-1) depends ontemperature according to exp = 76.6 exp (-1708/T), withT in kelvin. Our parametrization predicts that the SSA ofa snow layer evolving at - 40 C will decrease by a factorof 2 after 14 days, while a similar decrease at -1 Cwill only require 5 days. Wind was found to increase therate of SSA decrease, but insufficient data did not allow aparametrization of this effect.