The ratio of flux density (often given in units of )
of a substance at a sink surface to its concentration in the atmosphere (corresponding units of ).
While the units of this ratio are clearly those of velocity (in this case ),
the ratio is not a flow velocity in the normal sense of the word.
PAC, 1990, 62, 2167
(Glossary of atmospheric chemistry terms (Recommendations 1990))
on page 2184
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. doi:10.1351/goldbook