Turbulent Exchange of Momentum and Scalars in the Surface Layer over Antarctic Snow and Ice

Abstract

Vertical profiles of wind speed, temperature and humidity were used to estimate the roughness lengths for momentum (z.₀), heat (z._H) and moisture (z._Q) over Antarctic surfaces. The vertical profile-measurements were performed on and near a blue ice field in Queen Maud Land, East Antarctica. The roughness lengths are generally used to compute the fluxes of momentum, heat and moisture from standard meteorological observations using the flux-profile relationships. The value of z₀ is easily evaluated from the wind speed profile. The scalar roughness lengths are evaluated using a new method, which circumvents the difficult measurement of the surface temperature. It is found that the vertical exchange processes are strongly influenced by the saltating snow particles close to the surface during snow-drift events. The scalar roughness lengths seem to be approximately equal to z.₀ for a large range of roughness Reynolds numbers, despite the frequent occurrence of drifting snow. It is suggested that snow-drift processes are important for the turbulent transport of scalar quantities such as heat and water vapour, and presumably also for the transport of other atmospheric constituents.

This contribution is based on the paper ‘Momentum and scalar transfer coefficients over aero dynamically smooth Antarctic surfaces’ by R. Binlanja and M.R. van den Broeke, which will be published in Boundary-Layer Meteorology. The material used here is reprinted by permission oí Kluwer Academic Publishers.