THE BAROCLINIC, VARIABLE EDDY VISCOSITY EKMAN LAYER - AN APPROXIMATE ANALYTICAL SOLUTION

The WKB method is used in conjunction with the variation of parameters technique to find an approximate analytical solution for Ekman layers with eddy viscosity and horizontal pressure gradient that are each va riable with height from the surface. Behaviour of the solution is illu strated by comparing model output when several eddy viscosity and hori zontal pressure gradient profiles are used. Cases where the pressure g radient decreases with height accentuate the super-geostrophic peak in the wind velocity profile, with decreasing eddy viscosity with height further enhancing this effect. Increasing pressure gradient with heig ht reduces or eliminates the peak. The model output when using an eddy viscosity that has a low-level peak fits marine boundary-layer data t aken during ASTEX better than the classic solution - the model giving greater low-level mixing which is seen in ASTEX data as well as in dat a from ERICA.