Abstract <p>A mechanism for reducing the ocean surface drag coefficient at an extremely high wind velocity, as detected by processing the GPS data from falling surface probes, is proposed. The momentum exchange between the atmosphere and spray drops at a high wind velocity leads to deformation of the wind velocity profile in the atmospheric boundary layer due to momentum extraction by the drops. This deformation increases rapidly when the spray generation process is activated through the bag-breakup fragmentation, which leads to the formation of a great number of large drops levitating in the air flow during hurricane-force winds. The logarithmic approximation of the wind velocity profile in the profiling method yields effective values of dynamic velocity, roughness parameter, and aerodynamic drag which are reduced compared to their true values. The calculated effective parameters of the turbulent boundary layer are in good agreement with the experimental data on hurricane-force wind velocity.</p>

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Drop Effect on the Air Flow Structure in the Surface Boundary Layer of the Atmosphere during a Hurricane

  • Yu. I. Troitskaya,
  • A. N. Zotova,
  • D. A. Sergeev

摘要

Abstract

A mechanism for reducing the ocean surface drag coefficient at an extremely high wind velocity, as detected by processing the GPS data from falling surface probes, is proposed. The momentum exchange between the atmosphere and spray drops at a high wind velocity leads to deformation of the wind velocity profile in the atmospheric boundary layer due to momentum extraction by the drops. This deformation increases rapidly when the spray generation process is activated through the bag-breakup fragmentation, which leads to the formation of a great number of large drops levitating in the air flow during hurricane-force winds. The logarithmic approximation of the wind velocity profile in the profiling method yields effective values of dynamic velocity, roughness parameter, and aerodynamic drag which are reduced compared to their true values. The calculated effective parameters of the turbulent boundary layer are in good agreement with the experimental data on hurricane-force wind velocity.