It is traditional in courses on air pollution to consider the shape of smoke plumes from chimneys in relation to air pollution. Indeed it is often easy to spot someone on a train who has some experience in air pollution dispersion. The temptation to plume spot is sometimes irresistible and often entertaining.

The author recalls whiling away the time whilst flying from Chicago to Atlanta watching plumes from the air and being able to identify easily the lapse rates into which the plumes were being emitted (and he was not wearing an anorak at the time).

We should remember that this plume behaviour occurs even when the plume is not visible, and that knowledge of the lapse rate can often help us predict when pollution problems may occur.

The atmospheric lapse rate will affect the way in which plumes are dispersed.