The spreading or @S05487@ of a gaseous or liquid material. @E01888@ diffusion in the atmosphere is the process of transport of gases due to turbulent mixing in the presence of a composition @G02669@. Molecular diffusion is the net transport of molecules which results from their molecular motions alone in the absence of turbulent mixing; it occurs when the @C01227@ of a particular gas in a mixture differs from its equilibrium value. @E01888@ diffusion is the most important mixing process in the lower atmosphere, while molecular diffusion becomes significant at the lower pressures of the upper atmosphere.
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2185 [Terms] [Paper]