An inversion

The smoke from two bonfires at Foreland (burning grubbed-up gorse bushes) has risen in the still air this morning until it has reached the level at which the smoke temperature matches that of the air and, because it is no longer warmer than the air, it cannot continue upwards, but has spread out horizontally. What has happened is that there is a layer of warmer air sitting on top of a layer of cooler air which was chilled by the ground temperature last night, which was quite a cold one. Normally, air temperature drops as the altitude increases, but here, with no wind to mix the two layers together, the warmer air is above the cooler, which is known as a temperature inversion. It will only last until the layers have mixed, usually by the wind, and indeed one plume has already broken through.
Malcolm