Identifying the types of Cloud present

Height levels - the height range of clouds

Clouds are generally encountered over a range of heights between the ground and about 60,000 feet.  By convention, the atmosphere is vertically divided into three levels: high, middle and low.  Each level is defined by the range of heights at which clouds of a certain type occur most frequently. When the height of a cloud is known, a choice can usually be narrowed down to the cloud types normally encountered at that height.

The height ranges for the levels in the table below are derived from the Bureau's Surface Observations Handbook.

Level

Cloud Type

Height ranges (Australia)

High

Cirrus

Cirrocumulus

Cirrostratus

Above 20,000 ft

Middle

Altocumulus

Altostratus2

Nimbostratus1,2

8,500 ft - 20,000 ft

Low

Stratocumulus

Stratus

Cumulus2

Towering Cumulus2

Cumulonimbus2

Below 8,500 ft

1              Nimbostratus frequently occurs with a base below 8,500 ft (6,500 ft in Antarctica).

2              These clouds may extend through two or all three étages  

Cloud types can occur outside these height ranges depending on location, season and influencing air mass. It is common, for instance, for the base of ‘low’ cumuliform clouds to occur well above 8500ft in inland Australia during the warmer months.

The WMO Cloud Atlas cloud height table below shows an overlap of the levels with their limits varying between polar, temperate and tropical regions of the world. Observers may find this table helpful in situations where the Australian region levels (above) are inadequate.

Level

Cloud

Polar region

Temperate region

Tropical region

High

Cirrus
Cirrocumulus
Cirrostratus

10 000 – 25 000 ft

16 500 – 45 000 ft

20 000 – 60 000 ft

Middle

Altocumulus
Altostratus
Nimbostratus

6 500 – 13 000 ft

6 500 – 23 000 ft

6 500 – 25 000 ft

Low

Stratus
Stratocumulus
Cumulus

Towering Cumulus
Cumulonimbus

Surface – 6 500ft

Surface – 6 500ft

Surface – 6 500ft