Cumulus Clouds

Cumulus is the result of convection. The ground is heated and masses of warm air, thermals rise. The thermals mix with the surrounding air which is drier, and the cloud evaporates. The rising parts have sharply outlined tops and are very white. The evaporating parts are ragged and of a duller colour.

Cumulonimbus is the name given to cumulus from which rain is falling. This picture shows a large example which is partly glaciated at the top. At a much higher level a thin layer of cirrus cloud (made of ice cyrstals) can be seen.

Cumulonimbus produces an ice anvil if it spreads out at a stable layer after becoming glaciated. The nearest tower has pileus on it as it pushes up a short distance into the stable layer before sinking back and spreading out as an ice anvil.

A pileus or cap cloud often appears on the top of a thermal. This cumulus is being produced from thermals rising off the east side of a hill which is the first place to be warmed in the morning.