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1. Polydisperse Sea Spray Effect on the Vertical Momentum Transport in Hurricanes

   https://doi.org/10.1175/JAS-D-23-0195.1  

   Rastigejev, Yevgenii; Suslov, Sergey_A (July 2024, Journal of the Atmospheric Sciences)

   Abstract This study focuses on the influence of the sea spray polydispersity on the vertical transport of momentum in a turbulent marine atmospheric boundary layer in high-wind conditions of a hurricane. The Eulerian multifluid model treating air and spray droplets of different sizes as interacting interpenetrating continua is developed and its numerical solutions are analyzed. Several droplet size distribution spectra and correlation laws relating wind speed and spray production intensity are considered. Polydisperse model solutions have confirmed the difference between the roles small and large spray droplets play in modifying the turbulent momentum transport that have been previously identified by monodisperse spray models. The obtained results have also provided a physical explanation for the previously unreported phenomenon of the formation of thin low-eddy-viscosity “sliding” layers in strongly turbulent boundary layer flows laden with predominantly fine spray. Significance StatementAchieving better accuracy in hurricane forecasts requires an in-depth understanding and accurate modeling of the ocean spray effect on the vertical fluxes of momentum and heat in a hurricane boundary layer. It has been shown that this effect depends on the size distribution of spray droplets, also known as spray polydispersity. This study aims to investigate the influence of a polydisperse spray on the vertical momentum transport within hurricane boundary layers by employing a modern theory of turbulent disperse multiphase flows. 

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2. Sensitivity of Sea‐Surface Enthalpy and Momentum Fluxes to Sea Spray Microphysics

   https://doi.org/10.1029/2021JC017774  

   Sroka, Sydney; Emanuel, Kerry (December 2021, Journal of Geophysical Research: Oceans)

   Abstract Accurate estimates of air‐sea enthalpy and momentum fluxes are critically important for hurricane intensity predictions. However, calculating these fluxes is challenging due to the nature of the air‐sea transition region. At extreme wind speeds, a substantial amount of sea spray is lofted making it necessary to calculate the sea spray‐mediated enthalpy and momentum fluxes. These calculations rely on microphysical equations, which are sensitive to the details of the local environmental conditions. Here we use a microphysical model to show that there exists a threshold wind speed beyond which the net sea spray‐mediated enthalpy and momentum fluxes are well‐approximated by using the net sea spray mass flux alone. This result supports the hypothesis that at extreme wind speeds, the ratio of the air‐sea exchange coefficients becomes independent of wind speed, implying the air‐sea flux calculations can be substantially simplified. 

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3. Eddy Influences on the Hadley Circulation

   https://doi.org/10.1029/2018MS001554  

   Davis, Nicholas A.; Birner, Thomas (June 2019, Journal of Advances in Modeling Earth Systems)

   Abstract Variations in the width and strength of the Hadley cells are associated with many radiative, thermodynamic, and dynamical forcings. The physical mechanisms driving these responses remain unclear, in part because of the interactive nature of eddy‐mean flow adjustment. Here, a modeling framework is developed which separates the mean flow and time‐mean eddy flow in a gray radiation general circulation model with simple representations of ocean heat transport and ozone. In the absence of eddies, with moist convection and weak numerical damping, the Hadley cell is confined to the upper troposphere and has a vanishingly small poleward momentum flux. Eddies allow the cell to extend down to the surface, double its heat transport, and flux momentum poleward, the latter two being basic consequences of a deepening of the circulation. Because of convection and damping—which mimics, in part, the effect of eddy stresses—previous work may have underestimated the impact of eddies on earth's circulation. Quasigeostrophic eddy fluxes are sufficient to produce Hadley and Ferrel cells, but with a substantially greater Hadley cell strength than when all eddy impacts are considered, including eddy fluxes of moisture, mass, and momentum and eddy impacts on surface fluxes and clouds. 

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4. Flux-based modeling of heat and mass transfer in multicomponent systems

   https://doi.org/10.1063/5.0085444  

   Beris, Antony N.; Jariwala, Soham; Wagner, Norman J. (March 2022, Physics of Fluids)

   In the present work, the macroscopic governing equations governing the heat and mass transfer for a general multicomponent system are derived via a systematic nonequilibrium thermodynamics framework. In contrast to previous approaches, the relative (with respect to the mass average velocity) component mass fluxes (relative species momenta) and the heat flux are treated explicitly, in complete analogy with the momentum flux. The framework followed here, in addition to allowing for the description of relaxation phenomena in heat and mass transfer, establishes to the fullest the analogy between all transport processes, momentum, heat, and mass transfer, toward which R. B. Bird contributed so much with his work. The inclusion of heat flux-based momentum as an additional variable allows for the description of relaxation phenomena in heat transfer as well as of mixed (Soret and Dufour) effects, coupling heat and mass transfer. The resulting models are Galilean invariant, thereby resolving a conundrum in the field, and always respect the second law of thermodynamics, for appropriate selection of transport parameters. The general flux-based dynamic equations reduce to the traditional transport equations in the limit when mass species and heat relaxation effects are negligible and are fully consistent with the equations established from the application of kinetic theory in the limit of dilute gases. As an added benefit, for the particular example case of hyperbolic diffusion we illustrate the application of the proposed models as a method to allow the use of powerful numerical solvers normally not available for solving mass transfer models more generally. 

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5. A Review of Parameterizations for Enthalpy and Momentum Fluxes from Sea Spray in Tropical Cyclones

   https://doi.org/10.1175/JPO-D-21-0023.1  

   Sroka, Sydney; Emanuel, Kerry (June 2021, Journal of Physical Oceanography)

   Abstract The intensity of tropical cyclones is sensitive to the air-sea fluxes of enthalpy and momentum. Sea spray plays a critical role in mediating enthalpy and momentum fluxes over the ocean’s surface at high wind speeds, and parameterizing the influence of sea spray is a crucial component of any air-sea interaction scheme used for the high wind regime where sea spray is ubiquitous. Many studies have proposed parameterizations of air-sea flux that incorporate the microphysics of sea spray evaporation and the mechanics of sea spray stress. Unfortunately, there is not yet a consensus on which parameterization best represents air-sea exchange in tropical cyclones, and the different proposed parameterizations can yield substantially different tropical cyclone intensities. This paper seeks to review the developments in parameterizations of the sea spray-mediated enthalpy and momentum fluxes for the high wind speed regime and to synthesize key findings that are common across many investigations. 

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