Modeling Sea Spray Influence on Vertical Enthalpy and Momentum Transport in Hurricanes with the Multifluid Approach

Abstract A multifluid model of the hurricane boundary layer laden with evaporating sea spray has been developed to enable an in-depth investigation of the spray effect on the vertical heat and momentum exchange. This model accounts for several important physical processes, particularly those associated with the relative motion between air and droplets, that conventional mixture-type models cannot capture. Although both the multifluid and mixture models predict qualitatively similar spray influences on boundary layer characteristics and the vertical transport of heat and momentum, their quantitative results differ noticeably due to the additional physics incorporated in the multifluid approach. Using the multifluid framework, the study examines the influence of sea spray on bulk enthalpy transfer, air–sea drag coefficients, and their ratio. Notably, at hurricane wind speeds, the ratio of the bulk enthalpy transfer and air–sea drag coefficients in a spray-laden atmosphere is nearly double that in spray-free conditions, reaching values in the range of 0.6–0.75. These results agree well with both existing measurements and theoretical estimates based on the hurricane energy budget. Furthermore, the analysis reveals that both bulk enthalpy transfer and air–sea drag coefficients decrease when the droplet injection speed increases. Significance Statement Accurately predicting hurricane and severe storm characteristics is crucial for protecting lives and property. To do this, an in-depth knowledge of all key physical processes that influence storm behavior is required. The role of sea spray in hurricane dynamics has remained poorly understood. The current study addresses this aspect by introducing an advanced multifluid model that captures sea spray effects on the turbulent heat and momentum exchanges between the ocean and the atmosphere. The results show that predictions of the multifluid model align well with field observations and are more accurate than those of the mixture counterpart.