From Glossary of Meteorology


The nearly equal vertical and lateral dispersion of air pollutants from the centerline of a smoke plume, which occurs in statically neutral conditions (
see static stability).

As pollutants from a point source are blown downwind, the envelope of the smoke plume (as visible by eye or as measured by the percentage decrease of concentration from that at the centerline) takes the shape of a cone. Conversely, observation of a coning smoke plume can be used as an indicator that the ambient air there is statically neutral.
Compare fanning, looping, fumigation.