A numerical study of the wind field in a typhoon boundary layer

The wind held in a typhoon boundary layer (TBL) has been investigated by a numerical model. The results show that vertical profiles of wind speed in the TBL can be satisfactorily stated by conventional power-law expressions. To describe the structure of strong wind in the TBL, two parameters have been suggested: one is a dimensional parameter, f(lambda), approximately representing the absolute vorticity in the wind field, and the other is a non-dimensional parameter, xi, characterizing the heterogeneity of vorticity in the radial direction of a typhoon. Substituting the parameter f(lambda) by Coriolis parameter f, the gradient height z(g) during typhoons can be predicted by the same formula as that used during non-typhoon climates. The ratio of surface to gradient wind speeds G(r) and the inflow angle gamma(s) in the TBL are also examined using the present numerical results, and the formulae for predicting them are presented.