Profiles of mean wind and turbulence intensity during strong typhoon landfall

Abstract

It is established that the mean wind in a typhoon structure is related to the typhoon intensity ΔP and the normalized distance D/Router between the typhoon center and observation spot. To further investigate the influence of ΔP and D/Router on extreme winds under typhoon conditions, field measurements of mean wind speeds U and turbulence intensities Iu at different heights below 70 m during the strong typhoons Haitang, Matsa, and Khanun were carried out during the landing process along the southeast coastline of China. It was concluded based on analyses that the profiles of U and Iu in typhoon conditions can be approximated by a power law. Furthermore, most of their exponents about mean wind αU and ones about turbulence intensity αIu are significantly larger than the code value of 0.12 in terrain A. The αU and αIu during the three strong typhoons fluctuated roughly before landing and linear stationary variation after landfall. After landing, αU decreased with U and ΔP for the three typhoons. αU increased with D during the typhoons Matsa and Khanun, whereas it decreased with D/Router during Haitang. After landfall, αIu decreased with ΔP and increased with D/Router during Matsa and Khanun, whereas it varied in a converse manner during Haitang.