Some investigations into drifting snow and its sublimation in the turbulent atmosphere boundary layer

Ning Huang 1 ,2, Guang Li1 ,2, Zhengshi Wang1 ,2
1Key Laboratory of Mechanics on Disaster and Environment in Western China (Lanzhou University), The Ministry of Education of China, Lanzhou, China, 2Department of Mechanics, School of Civil Engineering and Mechanics, Lanzhou, China

The drifting snow and its phase transition process are of vital importance on the polar ice sheet mass balance and cold region hydrology distribution. Whereas, the influences of atmospheric turbulence on the movement of saltating snow and the formation of blown snow are little known for in current drifting snow models the air flow are mostly taken as temporal average flow. Furthermore, the saltation snow particle sublimation is usually neglected because scientists thought that the atmosphere humidity will soon reach saturation in the saltation layer. In this paper, the turbulent atmosphere boundary layer is generated by a modified Large Eddy Simulation (LES) code of ARPS (version 5.3.3). The drifting snow with mixed grain size is produced and the coupling effects between wind field and snow particles are taken into account. The processes of aerodynamic entrainment and particle-bed interaction as well as the 3-D trajectory of every snow particle are considered. The drifting snow sublimation is included through a mass change of mid-air snow grains and its feedback effects on the temperature and moisture fields are implemented. The results indicate that the saltating snow particles in the turbulent flow form obvious banded structures. The snow streamers are proved mainly the reflection of downwind turbulent structures and the near wall wind feature has better relevancy with the drifting snow structure. The saltation snow particle sublimation will continually happen because of the impact of moisture advection and diffusion mechanisms, and therefore the saltation sublimation contributes a large proportion of the total sublimation.