Vertical distribution characteristics of the typhoon gust factor based on a 356-m high meteorological gradient tower

The characteristics of typhoon gust factors (GF) are important for the design of high-rise buildings in coastal areas. Most research on GF are based on observational data near the ground. This has made it difficult to meet the increasing demand for high-rise building designs in recent years. Thus, improving the knowledge of the vertical distribution of GF inside the typhoon is necessary and helpful for the design of high-rises and the prevention of gust disasters. In this study, the data from a 365-m high meteorological tower were used to explore the vertical distribution features of the gust factor within the atmospheric boundary layer (ABL) of typhoons in coastal region. The results indicate that: (1) The statistical probability distribution of GF during the typhoon exhibits a non-Gaussian distribution at all observational heights of the tower. While the generalized extreme value distribution (GEV) can well describe the properties of the probability distribution of GF at different heights. (2) The GF have a weak relationship with the average wind speed. However, GF have a strong relationship with turbulence intensity and increases linearly with the turbulence intensity. Notably, the results from the previous empirical model of the GF do not fully match the parameterised results during typhoons in this study. (3) In the typhoon boundary layer, the bulk wind shear plays a significant role in generating turbulent eddies with scales comparable to the observation height, especially at lower layer. Besides, the strong turbulent fluctuations at near-ground layers may be a result of the coupling of several elements. The turbulent momentum flux transported downward from the upper layers has a significant impact on the peak gust, and the downward transported energy may further enhance the turbulent motion in lower layers, which may lead to a higher gust factor near the surface.