Estimation of the height of the cloud base

Aerological diagram

The presence of layer clouds on an aerological diagram is indicated by spikes or broader areas with a reduced dew point depression. The height of the base of the cloud can be determined from the vertical axis of the diagram. Further, the actual value of the dew point depression gives an approximation of cloud coverage:

Dew Point Depression

Cloud Cover

0 to 2°C

Overcast layer

3 to 5°C

Broken thick layers

6 to 10°C

Scattered thin layers

> 10°C

No layer cloud

As well as an indication of height, the aerological diagram will show the temperature of the cloud layer which can assist with identifying the cloud type. See the example below.


aerological diagram cloud height information

*Note: The height scale indicates heights above mean sea level in a standard atmosphere. Elevation must be taken into account when converting the height to above station level.

Aerological diagrams are generally available at capital city airports as well as a number of other key locations. Radiosondes are typically launched at 2315hrs UTC and are available on the Bureau’s external website a couple of hours later. Some locations also release a radiosonde at 1115hrs UTC. 

The aerological diagrams are available from the following web address: http://www.bom.gov.au/aviation/observations/aerological-diagrams/

More information about aerological diagrams can be found here: http://www.bom.gov.au/aviation/data/education/skew-t.pdf