An analytical model on the simulation of the wind field in a typhoon boundary layer

Abstract

An analytical model has been developed for calculating the velocity field in a moving typhoon boundary layer. The present model has an upper inviscid region of cyclostrophic balance and a lower friction region controlled by surface drag coefficient and eddy viscosity. The velocity in the inviscid region is first described using an assumption that wind field moves with translation velocity of typhoon. A perturbation analysis is then perfonned to obtain the tangential and radial boundary layer velocity in the friction region. Validation of the model is carried out by comparing observed wind speed and direction records obtained from three typhoons in 1991 to those predicted by the model itself. The wind velocity and direction predicted are in good agreement with those observed at a one-hundred metre tall tower. Rapid variation of the wind velocity depends on the surface roughness and topograpy around the tower. Finally, a case study is conducted to examine the characteristis of the ratio of surface to gradient wind speeds G (r) and the inflow angle γ in the typhoon boundary. Previous typhoon observations data in coastal regions are well explained by this model.