An intercomparison of bulk aerodynamic algorithms over sea ice during the Surface Heat Budget of the Arctic Ocean experiment

In recent years, the Arctic has been recognized as an important part of the global climate system. An integral component of the climate system in the Arctic is sea ice. The presence of the ice fundamentally changes the energy and momentum exchange between the ocean and the atmosphere. Thus, an accurate representation of the surface turbulent fluxes in climate models is a necessity. An intercomparison of bulk aerodynamic algorithms that calculate surface turbulent fluxes in four climate and numerical weather prediction models is undertaken using data from the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment which occurred on an ice floe north of Alaska from October 1997 to October 1998. Comparison of the model-calculated fluxes with those observed during the experiment shows that some model algorithms produce substantially different sensible heat fluxes, latent heat fluxes, and wind stress for some stability and wind speed regimes. Large differences are also found by comparing the observed fluxes at several heights on a 20-m tower at the experiment site with algorithm-calculated fluxes. Further, the observed roughness lengths will be compared to those constants used in several of the model algorithms. Finally, suggestions will be made regarding how to improve the bulk algorithms as used in these weather and climate models.