Observation study on the turbulence characteristics of the boundary layer during strong Typhoon Muifa (2022)

Abstract

The increasing impacts of tropical cyclones (TCs) under climate change necessitate a deeper understanding of boundary layer turbulence dynamics, particularly in urban landscapes dominated by high-rise building clusters in the coastal megacities. This study investigates the turbulent characteristics within the TC boundary layer (within 400 m, TCBL) of Typhoon Muifa (2022) during its landfall in Shanghai, China, using synchronized Doppler wind lidar observations from two sites ~18 km apart: one site in Lujiazui, the dense downtown with dozens of skyscrapers, and the other in Baoshan, a rural countryside area. Key findings of this research reveal distinct turbulence regimes in the two environments. Maximum wind speeds were similar in the downtown (about 35 m s⁻¹) and the countryside (about 37 m s⁻¹), with downdraft magnitudes exceeding 5 m s⁻¹ (Downtown) and 6.8 m s⁻¹ (Countryside), respectively. The turbulence kinetic energy (TKE) profiles diverged significantly: urban TKE exhibited a non-monotonic vertical structure, peaking at ~250 m before declining, whereas rural TKE decreased uniformly with height. Analysis of the estimable TKE budget terms identified shear production as the largest measurable source term of enhanced turbulence in the urban environment. This finding is consistent with the wind speed disparities and complex airflow interactions induced by building clusters. Meanwhile, the vertical advection term also was identified as a significant contributor in sustaining and developing turbulence. These results highlight the critical influence of urban morphology on TCBL dynamics, with implications for refining numerical simulations of wind fields, improving disaster resilience strategies for coastal megacities, and informing wind-resistant design standards for high-rise structures in typhoon-prone regions.

Graphical abstract

Keywords

typhoon / Doppler wind lidar / wind profile / turbulence kinetic energy / wind shear

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