ABSTRACT
The rigorous way of treating friction in the planetary boundary layer is by means of turbulence theory. This is a highly complex subject and we shall only touch on its simplest aspects in this work. We shall first, however, consider friction in a simpler way. Guldberg-Mohn assumed that surface friction could be parameterized by letting the frictional deceleration of the air be proportional to the wind velocity. Although the Guldberg-Mohn parameterization of friction is extremely convenient in some models, particularly in Lagrangian representations of motion, it does not embody the rigid mathematical physics of an exact explanation of the effect of friction. To do this we must venture into the field of turbulence, and consider that friction is due to the effects of eddy viscosity. In dealing with the surface layer we define a new and very important parameter called the friction velocity.
