Exchange processes at the air-snow interface

The air-snow interface is an important component that regulates different transfer processes between the cryosphere and the lower atmosphere. The snow cover plays, in fact, an important environmental role in absorbing and emitting energy, and in impacting polar atmospheric chemistry and oxidative capacity by adsorption/desorption of reactive species. This is the reason why the snow cover characterization and its annual spatial variability represent important factors to be considered for climate modeling at a global scale. The description of processes occurring at the air-snow interface requires a multi-disciplinary approach based on the characterization of the snow cover, on the definition of the meteo-climatological conditions and on the estimation of chemical fluxes. The first component requires information about the snow extent, the snow micro-physics and the surface roughness that can be obtained combining remote sensing, proximal sensing and ground observations. While satellite products are key data sources for the estimation of the snow cover extent at a regional scale, web cameras are innovative proxy for connecting snow products at different spatial resolutions. The development of automated algorithms has produced a significant added value for estimating the fractional snow cover over long time-series and for validating satellite products. Now, we are ready to collaborate with the Norwegian Polar Institute and other players to have multi-years descriptions of the snow cover. In addition-, we developed an important asset devoted to the description of the snow cover from an optical point of view. This step is very important since the snow optical behavior, especially in the near-infrared wavelength range, is strictly related to the specific surface area available between snow grains. This parameter represents the surface available to the radiative transfer and to the chemical exchanges. We are developing a technological infrastructure, named Continuous Reflectance Monitor (Snow-Ice CReM) that, in this case, is devoted to describe continuously whole-round-year the spectral behavior of the snow cover at the CCT Tower. The combination of the spectral behavior and the spatial distribution of the snow cover define the background input for modeling radiative and chemical fluxes at the interface. Meteo-climatology is another basic input that must be investigated in terms of atmospheric stability, long-range transport of air masses and vertical intrusions of katabatic winds. From this perspective, the Italian Arctic Station represents a key infrastructure where different data sources can be integrated and new assets can be developed in order to estimate such key information. We dedicated a strong effort on using chemical tracers in order to describe the meteo-climatological framework in a complex system such as the Kongsfjord area. From this perspective, radon represents a functional tracer for these purposes and we developed a routinely system for the estimation of the atmospheric mixing and the local-to-long-range behavior of air masses. The combination between the snow radiative behavior and the micro-meteorological context offers the opportunity to describe photochemical processes occurring at the interface. The adsorption/desorption of reactive gases (ozone, nitrogen species, oxidized organic compounds) are, in fact, controlled by the meteo-climatic conditions, the snow reflective behavior and by the thermodynamics of the involved chemical species as observed in recent observations. The contribution of air-snow exchanges on photochemistry and on the atmospheric oxidative capacity in the Arctic depends on the relation between the snowpack and the troposphere and on the temporal and spatial variabilities of major photochemically active species in snow and in air, such as NO, NO2, HONO, HNO3, particulate NO3-, volatile organic compounds (formaldehyde, acetaldehyde, acetone and carboxylic acids) and O3.