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Keywords:

  • bulk turbulent flux algorithm;
  • drag coefficient;
  • Ice Station Weddell;
  • roughness length;
  • SHEBA;
  • snow;
  • turbulence measurements

Abstract

A bulk flux algorithm predicts the turbulent surface fluxes of momentum and sensible and latent heat from mean measured or modelled meteorological variables. The bulk flux algorithm resulting from data collected over winter sea ice during SHEBA, the experiment to study the Surface Heat Budget of the Arctic Ocean, failed, however, in its first trial to predict the turbulent momentum flux over sea ice in the Antarctic. This result suggests that the main parameter for predicting the momentum flux, the aerodynamics roughness length z0, does not respond just to the friction velocity, as in the SHEBA algorithm, but is closely related to the physical roughness of snow-covered sea ice and may need to be site-specific. I investigate this idea with simultaneous measurements of z0 and the physical roughness of the surface, ξ, at Ice Station Weddell. The metric ξ derives from surveys of surface elevation and is related to but always less than the standard deviation in surface elevation. On combining the z0ξ pairs from Ice Station Weddell with similar data obtained over Arctic sea ice, I show that the Arctic and Antarctic z0ξ data lie along a continuum such that measuring ξ could provide a means for estimating a site-specific z0 for any global sea ice surface. Backscatter data from satellite-borne synthetic aperture radar might provide a remotely sensed estimate of ξ. Copyright © 2011 Royal Meteorological Society