Classification of Clouds in Australia
Clouds are formed when water vapour condenses into tiny water
droplets in the atmosphere. Of the entire weather phenomenon, clouds are
among the most attractive and interesting. Ranging from high altitude
cirrus to cirrostratus to the towering storm bearing cumulonimbus,
clouds are as varied as the weather itself.
There are mainly 10 types of clouds, which are further divided into 27
sub-types according to their height, shape, colour and associated
weather. Clouds are categorized as high (above 6 kilometres from the
earth's surface), low (to 2.5 kilometres) and middle (2.5 to 6
kilometres). It is an interesting fact that all clouds are white, but
when viewed from the ground some appear grey or dark according to their
depth and shading.
Different Cloud Types
Although clouds in the sky seem to be very different, it is possible to
classify them by common characteristics into several categories. The
classification, which is based on the shape and altitude of the clouds,
gives us the following groups of high clouds, middle clouds, and low
clouds.
High clouds are grouped together under a general name of cirrus. This
group includes cirrus, cirrocumulus, and cirrostratus. In temperate
latitude, these clouds shares an altitude of 5 and 13 kilometres and in
the tropics between 6 and 18 kilometres and polar regions between 3 and
8 kilometres.
Cirrus clouds, better known as "white clouds," are formed by ice
crystals. They occur either individually or in groups, have a fibrous
appearance, silky glow in the sunlight, and are surrounded by white
reflections.
Cirrocumulus clouds, also called high fleecy clouds, occur
infrequently. They are formed by ice crystals. They form ribbed
appearance, and join in groups, forming cloud fields.
 Cirrostratus clouds are also described as high cloudy veil, or
high cloudiness. This type of clouds consists mainly of ice crystals and
forms thin, expansive cloudy veils, reducing the intensity of the
sunlight. If these clouds cover the sun or the moon, they create a light
circle around these heavenly bodies.
The Middle clouds are found in an altitude of approximately 3 to 4
kilometres. They often originate from the cirrocumulus clouds and create
grey like layers covering large areas of the sky. These large clouds are
made up of water droplets and ice crystals. They signal the arrival of
rain. If, due to high rate of evaporation, the rain does not reach the
ground, they form fringes on the lower edges.
Low clouds occur at the altitude of up to 2 kilometres. They include
stratocumulus and stratus clouds. They extend from the vicinity of the
ground to about 2000 meters above ground. Because of that, they are
sometimes called high fog. Their base structure is not well organized
and they give the impression of grey foggy mist. Such clouds consist of
droplets and at lower temperature, they form ice crystals. At times,
when these clouds are very dense they may produce drizzle or sometimes
even tiny particles of snow.
A good example of such low clouds is Cumulus clouds. They are also
called dome-shaped clouds. The upper part glows with white light, the
lower portion is often dark. These clouds form when the ground is
heated, most often in the afternoon and in summertime.
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