A GENERATION-DISPERSION MODEL OF AMBIENT AND TRANSIENT BUBBLES IN THE CLOSE VICINITY OF BREAKING WAVES

Bubble models are necessary to ascertain bubble contribution to ocean-atmosphere fluxes of gas, aerosols, humidity, and latent heat. Previous theories flatten the wave breaking layer to a theoretical boundary from which bubbles are dispersed by turbulence working against buoyancy lift. As a consequence, bubble population characteristics next to the surface are not derived from these models but depend on empirical or semiempirical assumptions made at this boundary. By considering bubble injection with puffs of intense turbulence, specifying how bubbles are first created by a small-scale similarity reasoning, and using a wavy interface, the present bubble theory expands this layer to a more physical breaking layer. Bubble concentration density as a function of bubble diameter, depth, and sea state parameters is obtained through explicit integrals. The model is found to be consistent with the previous bubble theories: the back flattening of the model breaking layer indeed results in equations compatible with these theories. The model variations in bubble concentration density with different parameters is coherent with experimental laws: the dominant bubble concentration is found to vary as about d-4 with bubble diameter and u*3 with wind friction velocity, but because of breaking patches, a d-2 bubble distribution is obtained very close to the surface. The concordance of the model with experimental data in the recent and classic bubble literature is quite good.