deposition velocity

in atmospheric chemistry
The ratio of flux density (often given in units of g cm-2 s-1) of a substance at a sink surface to its concentration in the atmosphere (corresponding units of g cm-3). While the units of this ratio are clearly those of velocity (in this case cm s-1), 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 (