The spreading or scattering
of a gaseous or liquid material. Eddy
diffusion in the atmosphere is the process of transport of gases due to turbulent
mixing in the presence of a composition gradient
. 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 concentration gradient
of a particular gas in a mixture differs from its equilibrium value. Eddy
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
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook