Moisture in the atmosphere - Fundamentals of the Physical Environment - page 71

Plate 4.5 Altocumulus cloud. It forms at middle levels of the atmosphere and shows some signs of weak convection.
Photo: Peter Smithson

(a)

(b) Wind speed

Erosion of
cloud growth

Condensation level

Invisible thermals
of warm air

(c) Dry air or weak instability
"Fair weather cumulus"

(d) Moist air and strong instability

Inversion

Condensation level

Figure 4.7
Atmospheric factors affecting
the form of cumuliform clouds.