Sea Surface Roughness and Drag Coefficient under free Convection Conditions

摘要

This paper investigates the sea surface roughness and the drag coefficient under free convection conditions. Two different approaches have been used to estimate the sea surface roughness. One approach is to assume that the sea surface roughness is aerodynamically smooth (i.e., z_o ～ v/u*). In the other approach, the sea surface roughness is related to the convective velocity scale. The Businger-Dyer formula for the non-dimensional wind shear and one other formula that has the non-dimensional form of the wind shear with the exponent of -1/3 are used to derive the minimum stability length, the minimum friction velocity, and the drag coefficient under free convective conditions. The results indicate that under free convection conditions, the convective processes enhance the surface roughness and also increase the locally induced wind stress in connection with the large-scale eddies in the convective boundary layer.