Blowing snow modelling and parameterization

Stephen J. Déry and M. K. Yau


The process of blowing snow is recognized as an important agent in the water and energy budgets of high-latitude regions such as the Mackenzie River Basin (MRB). By the transport of snow and concurrent sublimation, blowing snow can act as a substantial source of atmospheric water vapour and sink of mass at the Earth's surface. Recently, there has been much discussion on the magnitude of blowing snow fluxes which has led to the development of a number of numerical models that depict this process. Once such model is the time- or fetch-dependent PIEKTUK model of Déry et al. (1998) which incorporates a spectral distribution of suspended ice particles as well as the thermodynamic feedbacks of the sublimation process on the temperature and moisture profiles. For typical conditions encountered in the MRB, transport and sublimation rates of blowing snow are forecast to increase non-linearly with wind speed. It is found, however, that the sublimation process is self-limiting despite ongoing transport of snow by wind due to the inclusion of the thermodynamic feedbacks in the model. Further research has shown that bulk modelling of blowing snow is possible using an effective terminal velocity for the distribution of suspended particles. We will discuss how this allows blowing snow to be parameterized in the Canadian mesoscale compressible community (MC2) model. Some initial results on the effects of including blowing snow in this modified version of MC2 will be presented.