Analytical and computational modeling of the mechanical effect of polydisperse sea spray on hurricane dynamics
ORAL
Abstract
Accurately predicting the track and intensity of hurricanes and severe storms is essential for mitigating the risk of destruction they can cause. Sea spray influences the dynamics of hurricanes thermodynamically and mechanically by modifying the vertical enthalpy and momentum fluxes within the marine atmospheric boundary layer (MABL). The current study focuses specifically on the mechanical effect of a polydisperse spray. To investigate this effect, we employ the Eulerian multi-fluid method that treats air and droplets of different sizes as separate interacting and interpenetrating turbulent continua. Each continuum is characterized by its own velocity and turbulent kinetic energy and satisfies the mass and momentum conservation laws. A multifluid E-epsilon (aka k-epsilon) model serves as the turbulence closure. By utilizing data available in the literature, we have constructed and analyzed several spectra of the droplet size distribution and correlation laws that relate wind speed and spray production intensity. We have also considered two different models for the sea surface aerodynamic roughness length. Our findings demonstrate that the effect of spray on the vertical transport in MABL sensitively depends on the droplet size distribution and spray production intensity but only weakly on the choice of the aerodynamic roughness length model. Our numerical calculations have revealed the possibility of the formation of a thin "sliding layer" above wave crests that is characterized by low turbulent eddy viscosity. This layer emerges when a substantial amount of spray containing a large fraction of fine droplets disrupts turbulence through air-droplet friction. Consequently, the sliding layer, where the vertical turbulent transport is reduced due to low turbulent eddy viscosity, effectively isolates the bulk of the boundary layer from the rough sea surface ultimately leading to the crisis of the drag coefficient.
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Publication: Rastigejev, Y. and S. A. Suslov, 2023: Effect of sea spray polydispersity on the vertical momentum transport in a hurricane, submitted to J. Phys. Ocean.<br>Rastigejev, Y. and S. A. Suslov, 2022: Investigation of sea spray effect on the vertical momentum transport using an Eulerian multi-fluid-type model, J. Phys. Ocean., 52, 99-117. <br>Rastigejev, Y. and S. A. Suslov, 2019: Effect of Evaporating Sea Spray on Heat Fluxes in a Marine Atmospheric Boundary Layer, J. Phys. Ocean., 49, 1927-1948<br>Rastigejev, Y. and S. A. Suslov, 2016: Two-temperature non-equilibrium model of a marine boundary layer laden with evaporating ocean spray under high-wind conditions. J. Phys. Ocean., 46, 3083-3102. <br>Rastigejev Y. and S. A. Suslov, 2014: E-epsilon model of spray-laden near-sea atmospheric layer in high wind conditions. J. Phys. Ocean., 44, 742-763. <br>Rastigejev Y., S. A. Suslov, and Y.-L. Lin, 2011: Effect of Ocean Spray on Vertical Momentum Transport under High-wind Conditions. Boundary-Layer Meteorology, 141, 1-20.
