Convective instability of air in snow

Convective instability of air in the pores between ice crystals in snow is considered. In the Boussinesq approximation, a system of equations that describes the origin of thermal convection within the snow thickness is derived. It is shown that for snow, as for a liquid, there is a criterial number analogous to the Rayleigh number that determines the origin of air instability in snow. The contribution of natural convection of air to the heat- and mass-transfer processes in snow is estimated and possible reasons for the considerable scatter of reported experimental data on the thermal conductivity and diffusivity of snow are discussed.