Characteristics of the vertical wind profile in neutrally atmospheric boundary layers

Abstract

The wind field in a typhoon boundary layer (TBL) has been investigated by a numerical model. The results show that vertical profiles of wind speed and turbulence intensity in the TBL can be satisfactorily expressed by conventional power law expressions. Basic parameters in the expressions, with the exception of the gradient height zg, can also be predicted by formulas proposed in Part 1 of this paper. To describe characteristics of the TBL, two new parameters have been suggested: one is a dimensional parameter, fλ, representing the absolute vorticity in the wind field, and the other is a non- dimensional parameter, ζ characterizing heterogeneity of vorticity in the radial direction of typhoon. Substituting Coriolis parameter f with the parameter fλ, the gradient height zg during typhoons can be presented by the same formula as that during non-typhoon climates. The characteristics of the drag coefficient Cg (= u*/Ug) and the surface stress angle γs in the TBL are also examined using the present numerical model. The results indicate that Cg and rs are a function of a modified surface Rossby numeber Roλ(=Ug/(fλzo)) and the parameter ζ.