Abstract
Abstract. The study investigates the role of the air–sea interface using numerical simulations of Hurricane Arthur (2014) in the Atlantic. More specifically, the present study aims to discern the role ocean surface waves and sea spray play in modulating the intensity and structure of a tropical cyclone (TC). To investigate the effects of ocean surface waves and sea spray, numerical simulations were carried out using a coupled atmosphere–wave model, whereby a sea spray microphysical model was incorporated within the coupled model. Furthermore, this study also explores how sea spray generation can be modelled using wave energy dissipation due to whitecaps; whitecaps are considered as the primary mode of spray droplets generation at hurricane intensity wind speeds. Three different numerical simulations including the sea- state-dependent momentum flux, the sea-spray-mediated heat flux, and a combination of the former two processes with the sea-spray-mediated momentum flux were conducted. The foregoing numerical simulations were evaluated against the National Data Buoy Center (NDBC) buoy and satellite altimeter measurements as well as a control simulation using an uncoupled atmosphere model. The results indicate that the model simulations were able to capture the storm track and intensity: the surface wave coupling results in a stronger TC. Moreover, it is also noted that when only spray-mediated heat fluxes are applied in conjunction with the sea-state-dependent momentum flux, they result in a slightly weaker TC, albeit stronger compared to the control simulation. However, when a spray-mediated momentum flux is applied together with spray heat fluxes, it results in a comparably stronger TC. The results presented here allude to the role surface friction plays in the intensification of a TC.
Highlights
Extreme storms like hurricanes arise from the complex interactions among the various components within the earth system
We can see that the storm in the uncoupled model (Expt. 1) has a higher translation speed compared to the coupled atmosphere–wave model (Expt. 2–4) and best track data
Sea spray coupling (Expt. 3–4) does not have any appreciable effects on the model track, it does affect the translation speed of storm; in Expt. 3 the storm moves faster compared to Expt. 4
Summary
Extreme storms like hurricanes arise from the complex interactions among the various components within the earth system. Within the wave modelling community, wind forcing is considered to be the largest source of error, while in atmospheric modelling, sea surface parametrization has long been considered a reason for poor forecasts of storm intensity. Studies utilizing both idealized (Smith et al, 2014) and realistic model simulations (Green and Zhang, 2013) of hurricanes have demonstrated the sensitivity of the hurricane intensity to the surface layer parametrization schemes used in the model.
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