A relationship between the aerodynamic and physical roughness of winter sea ice

A bulk flux algorithm predicts the turbulent surface fluxes of momentum and sensible and latent heat frommeanmeasured ormodelled 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 z(0), 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 z(0) and the physical roughness of the surface, xi, at Ice Station Weddell. The metric. derives from surveys of surface elevation and is related to but always less than the standard deviation in surface elevation. On combining the z(0)-xi pairs from Ice StationWeddell with similar data obtained over Arctic sea ice, I show that the Arctic and Antarctic z(0)-xi data lie along a continuum such that measuring xi could provide a means for estimating a site-specific z(0) for any global sea ice surface. Backscatter data from satellite-borne synthetic aperture radar might provide a remotely sensed estimate of xi. Copyright (C) 2011 Royal Meteorological Society