Quantification of wind fluctuations in a Densely-built, urban district during a typhoon landfall by merging mesoscale meteorological and Large Eddy Simulations

Takemi, Tetsuya*; Yoshida, Toshiya   ; Duan, G.*

An intense tropical cyclone, Typhoon Jebi (2018) landed on the central part of Japan in September, caused severe damages due to strong winds in Osaka City. Buildings in urban areas are known to affect significantly the magnitude of wind gustiness. Thus, it is important to understand the underlying risks of wind damages derived from urban buildings. We investigate the influences of densely built urban environments on the occurrence of wind gusts in urban districts of Osaka City during the landfall of Typhoon Jebi by merging mesoscale meteorological and building-resolving Large Eddy Simulation (LES). The maximum wind gust in the analysis area is estimated as 60-70 m/s, which is comparable to the wind speed at the height of about 300 m. Instantaneous wind gusts are further examined in terms of building density and are found to become the strongest where the building density has a moderate value.