The Effect of Different Sea State Dependent Roughness Parameterizations on the Sensitivity of the Atmospheric Circulation in a Regional Model

An alternative approach for the parameterization of the air-sea momentum flux in the marine surface boundary layer was implemented into a regional coupled atmosphere-wave model. The sensitivity of the atmospheric circulation to this new parameterization was assessed and compared to two different approaches using Monte Carlo simulations. Two approaches explicitly use the sea state in the computation of the sea surface roughness, the third approach is the standard Charnock relation. It was found that parameters of the atmospheric circulation, such as 500 hPa gepotential height or monthly means of sea level pressure, show no substantial differences between all three parameterizations. This suggests that so far the computationally more economical Charnock relation represents a sufficiently reasonable parameterization of the momentum flux in regional climate models.