Calculation procedures are developed and results shown for the exact calculation of extinction and meteorological visual range using the blowing-snow mass in the atmosphere and particle radius. Results of the calculations show: (1) For monochromatic radiation, geometrical optics approximations of the extinction efficiency are found to provide results of only moderate accuracy in calculating the extinction of radiation by a single particle. (2) For broad-band radiation, the geometrical optics approximation is sufficiently accurate for many single-particle measurement instruments and applications, except in the infra-red band where Mie theory should be used. (3) For typical blowing-snow particle-size distributions, the shape parameter of the distribution of particle radii and the mean particle radius are very important in broad-band extinction and visual-range modelling. Estimates of blowing-snow quantities from broad-band extinction measurements or visual range from blowing-snow quantities should address the shape and mean value of the snow-particle radius distribution.

This physics-based two-phase flow model of the mass balance of drifting snow calculates the transport of snow through saltation and suspension, and recognizes the important role of in-transit sublimation on surface-erosion rates. Measurements of the vertical gradient of drifting snow-mass flux and wind speed in the surface-boundary layer indicate the total flux of saltating snow increases linearly with wind speed and is sensitive to the transport threshold. The total flux of suspended snow requires saltation to become established, and increases with the cube of both the total flux of saltating snow and the wind speed. The total suspended flux quickly becomes the dominant transport mode as wind speeds increase beyond threshold levels, and comprises more than 90% of the total flux for wind speeds greater than 15 ms−1. Sublimation rates estimated from wind speed, temperature, and humidity are sufficiently balanced by snow-surface erosion rates to ablate completely snow-packs with depths of the order 200 mm, a typical value for steppe and prairie environments.

During snowmelt over a continuous snow cover, the vertical turbulentexchanges of sensible and latent energy are influenced by regional air-masscharacteristics, which exert a strong control on air temperature. Inhigh-latitude sites, the melting surface rapidly becomes heterogeneous, withpatches of snow and snow-free areas. Local advection occurs whennear-surface air layers are warmed due to sensible heal flux from thesnow-free areas, with the resulting heat transferred horizontally toadjacent snowpatches. This advection greatly increases the rate of snowmeltalong the leading edges of the snowpatches. In order to estimate correctlythe average melt rates of the snowpatches and the bulk energy balance of theentire landscape, it is necessary to estimate the local advection component.To date, few studies have dealt with this problem. This paper reportsresults from an Arctic tundra site located approximately 55 km northeast ofInuvik, Northwest Territories, Canada. The importance of local advection isestimated by comparing the sensible heat flux of the snowpatches toestimates of sensible heat without local advection. This latter term isderived from a relationship between upper air temperature and sensible heatflux over a continuous snow cover. This work has important implications fordeveloping models that correctly represent the cryosphere of tundra regions,and in developing appropriate scaling techniques for heterogeneouslandscapes.