Characteristics of wind profiles in the landfalling typhoon boundary layer

• Studies are based on the data observed at six towers near three typhoon centers.
• There are differences in wind profiles at different portions of the typhoon.
• The wind profile exponents in the eyewall increase with the increasing wind speed.
• It proposes an empirical function to estimate the exponent of typhoon wind profile.
• The findings have important value for the safety of wind resistance.

In this study, representative characteristics of the observed typhoon winds along the coast of South China during the past 10 years are evaluated in accordance with different influences of rotational typhoon winds on engineering and structures. Three “ideal” typhoons, i.e., Hagupit, Nesat and Rammasun, whose core regions passed across six towers are selected. Statistical analyses, and curve-fitting are used to examine the structural evolution of the typhoon wind profiles; differences in intense winds occurring in the eyewall from those under nontyphoon flows; the impact of different surface roughness on the wind profile exponent (WPE). The strong wind profiles of the typhoon were found to deviate from the power law distribution by varying degrees. The deviation was more significant closer to the typhoon eyewall and eye region, and the maximum wind profile may potentially display a wake-like shape. The WPE varied markedly during the passage of a typhoon with the peak exponent at the radius of maximum wind. The power exponential function could relate well the wind profiles in the eyewall to the roughness length. This empirical function provides a simple and effective way to accurately estimate the power law exponent of intense wind profiles over the area influenced by typhoons.