Analysis of Nonstationary Typhoon Winds Based on Optimal Time-Varying Mean Wind Speed

The time-varying mean (TVM) component has a major influence on the characterization of nonstationary wind events and associated parameters of the fluctuating components. However, it is challenging to determine the optimal TVM of the nonstationary wind speed accurately due to variability in the low-frequency signal contents. To address this challenge, this study develops an effective wavelet-based method together with necessary conditions to calculate the optimal TVM from nonstationary wind speed data. For comparison, the time-dependent memory method is also used and enhanced to obtain the optimal TVM. Wind field turbulence characteristics of Typhoon Mangkhut are then analyzed and presented based on the conventional stationary model and nonstationary model with the proposed optimal TVM. In addition, this study also proposes an empirical description of the wind spectrum, which provides a better fit to the typhoon-related nonstationary winds than those offered by classical wind spectral description.