On the Production of Aitken Nuclei from Breaking Waves and Their Role in the Atmosphere

Abstract

A laboratory model of a breaking wave or whitecap was constructed, and the aerosol produced by it was investigated intensively. Submicron- and even Aitken-sized particles were produced: the presence of salt particles of mass <10?17 g(r<0.01 ?m) could be inferred. The evidence strongly suggests that the submicron fraction is composed of film drops, derived primarily from bubbles larger than 1 mm in diameter. The shape of the CCN spectrum and overall mass distribution of the model-produced aerosol were similar to what is observed in clean marine air. Whether or not the production rate of such small particles is globally significant when the model results are applied to the oceans depends to a large extent on the set of assumptions one makes concerning aerosol residence time and fraction of sea surface covered by whitecaps. However, there are realistic choices of these parameters which suggest that appreciable fractions of both CCN and CN in the lower marine atmosphere are produced directly by the sea.