Spectral modelling of typhoon winds considering nexus between longitudinal and lateral components

Abstract

The nexus between the spectra of longitudinal and lateral components is always neglected in the spectral modelling of typhoon winds. With spectral modification to the isotropic turbulence, a general model is developed for longitudinal and lateral spectra of typhoon winds considering their mutual nexus in this paper. Using the measured data of a landfall typhoon, the wind spectra are analyzed with comparisons to some widely utilized empirical formulas, and the adaptability of the general model is discussed. Due to the non-stationarity in the mean wind velocity, overfitting is encountered and the fitted model has large deviations from the measured spectra. Thus, a non-stationary wind velocity model is utilized, and the turbulence is treated in a semi-stationary manner. The general model can well describe the spectra of semi-stationary turbulence, and a unified semi-stationary model that adapts to different cases is then obtained. To further involve the time-varying properties of turbulence, the general model is extended into a time-frequency form to fit the measured evolutionary power spectral density (EPSD). The comparison between measured and fitted EPSDs verifies the effectiveness of the extended model that considers the nexus between longitudinal and lateral components at each frozen time.