Pyrocumulus Development
Question
If the atmospheric environment is favorable, cumulus may develop due to fires, as the lower tropospheric layer is heated, decreasing static stability:
The correct answer would be "True"
This can really happen! Then these clouds are usually called Pyrocumulus!
The satellite image below is from Meteosat 8 High Resolution Visible channel. The image shows several cumulus clouds on a hot day over the Iberian Peninsula in Spain and Portugal. The 1 km spatial resolution of this channel allows you to easily pinpoint individual clouds.
Click the image below and use right arrow until you reach the earth's surface. The latter three photos were taken from the surface on this day; one with several wild fires in Portugal. The photos show the development of a pyrocumulus cloud clearly. See how the dark smoke cloud grows vertically into a bright cumulus cloud!
Click to open gallery
Pyrocumulus definition
There is no official definition of pyrocumulus according to WMO. However, there are some definitions according to renowned meteorological institutions:
American Meteorological Society (AMS)
Pyrocumulus -
A cumulus cloud formed by a rising thermal from a fire, or enhanced by
buoyant plume emissions from an industrial combustion process.
MetOffice (UKMO)
Pyrocumulus - Cumulus
cloud that forms over an intense source of heat on the ground, such as
a heat of forest fire. (...) is an unhappy mixture of Greek and Latin.
Question
In which situations do you think smoke from fires may be retained in a certain tropospheric layer?
The correct answer is b).
In fact, when the atmosphere is stable, the risk for a dramatic growth of a pre-existing fire is low. However, due to the existence of an inversion layer, smoke is likely to be trapped below that layer. You will see an example in the next subchapter.