VIII. PLUMES OF SMOKESTACKS

A plume from an elevated source such as a tall exhaust stack mixes vertically and horizontally with ambient air as it drifts downwind, Vertical mixing is determined largely by the degree of instability of the lower troposphere. This depends upon the temperature profile. Horizontal mixture can also be influenced indirectly by the elapse rate. For a movement of air in the vertical direction cannot proceed without horizontal movement somewhere.