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\end{equation}  Considering the dependency of whitecap fractions on sea state as well, not only on wind speed, is essential in order assess their variability. Swells are are particular sea states that inhibit whitecap production. Because swells move faster than the environmental wind speed, they don't loose energy through wave energy dissipation (decisive in whitecap production), resulting in attenuated wave-breaking occurence. Swells generate a low level wave-driven supergeostrophic jet \cite{Hanley_Belcher_2008} that acts to disorganize eddies within turbulent flow at sea surface. This translates into removing friction caused by turbulent stress at sea surface, phenomenon responsible for foam cell rupture within whitecaps \cite{llaghan_Deane_Stokes_Ward_2012}, which decreases foam time decay. The amplitude of the swell, according to observations realized by Callaghan in 2012, can be calculated by integrating the wave spectrum between frequencies ${f}_{1}$ and ${f}_{2}$:   \begin{equation}  {a}_{w} a  = 2\sqrt{\int_{{f}_{1}}^{{f}_{2}}S(f)df}, \end{equation} where $S(f)$ is the wave spectral density.  Usually, a purely geostrophic horizontal wind at sea surface cannot inject enough turbulence to generate wave breaking. Therefore, a downward ageostrophic component or a shift from the purley geostrophy in the wind at sea surface should be present. The wave-driven supergeostrophic jet subdues the downward ageostrophic component (and enhances the upward ageostrophic component or the upward momentum flux), thus it reduces turbulent injection from atmosphere to ocean. The surface value of this wave-driven jet or stress can be described by integrating the wave-induced stress going into each wave component:  \begin{equation}