Clouds
are made up of millions of tiny water droplets which
form when moist warm air rises into the sky and is then
cooled down. If the cloud is really cold it is made up
of ice crystals. It can take between a few minutes and
an hour for a cloud to form.
Cloud classification
In 1803 a classification of clouds was
introduced by Luke Howard (1772-1864) who used Latin words
to describe their characteristics.
- Cirrus - tufts or whisps
- Cumulus - a heap or pile
- Stratus - a layer
- Nimbus - rain bearing
There are now ten basic cloud types with
names based on combinations of these words, along with
the word 'alto' which is now used to describe medium level
cloud.
These ten main cloud types can be separated
into three sections depending on how high their bases are
from the ground.
Low clouds
These are usually
made up of water droplets and have a base below 2,000
metres.
- Stratocumulus
- Stratus
- Cumulus
|
C.S. Broomfield (© Crown Copyright) |
Pictures
and descriptions of low clouds
Medium clouds
These are usually
made up of water droplets and have a base between
2,000 and 7,000 metres.
- Altocumulus
- Altostratus
- Nimbostratus
|
© D. Phillips |
Pictures
and descriptions of medium clouds
High clouds
Normally made up
of ice crystals, these have a base between 5,500
and 14,000 metres.
- Cirrus
- Cirrostratus
- Cirrocumulus
|
© R.K. Pilsbury |
Pictures
and descriptions of high clouds |
