FEATURES OF STRONG WIND PROFILES BY DOPPLER SODAR (PART 2)

- EXAMINATION OF MEAN WIND PROFILE BY PRINCIPAL COMPONENT ANALYSIS -

Abstract

The wind structures in the lower atmosphere has been investigated by Doppler sodar in Okinawa since 1994 associated with the wind resistant design of high-rise buildings. The measurements were carried out under strong wind conditions on both typhoon and non-typhoon days. It is suggested that the significant influence of the surface topography on the vertical distribution of the observed mean wind speed is limited in the lowest 100m above the ground at the observation site. In order to investigate the characteristics of the variations of wind profiles in typhoon and non-typhoon conditions, principal component analysis are applied to the observed data. The first principal components of typhoon and non-typhoon winds are found to be quite different from each other. According to the analysis, the vertical profiles of the non-typhoon winds seem to be mainly determined by the surface roughness, while the turbulence of the atmosphere aloft seems to contribute in a large degree in the formation of the typhoon wind profile. The latter is considered to be responsible for the decent of the layer with a constant wind speed of gradient wind to low altitudes often observed in typhoon conditions.