Guide to.......Clouds

[SP1986]

The Cloud Works

Clouds are simply condensed water droplets known as water vapour. These clouds can achieve many different things; they can give warnings, they can produce preciptation or merely tell how stable/unstable the atmosphere is. Clouds can come in many forms from the fluffy fair-weather Cumulus to the thick billowing frontal cloud of the Nimbostratus.

Fair-weather Cumulus are caused when the sun causes heating of the ground and this heat known as convection causes clouds to grow on the boundary between cool air and warm air and sometimes these fluffy fair-weather Cumulus can grow into Cumulonimbus causing heavy midday showers or evening thunderstorms.

Frontal cloud is the same process where warmer air bumps into cooler air or vica versa, causing moisture to form where the two air masses meet. This is also controlled by evaporating water from the sea/ocean before hand but only when a temperature gradient meet does condensation become very active and these two split areas of heat are called fronts.

The Cloud Types

Cirrus

Cirrus are wispy clouds. These clouds are made of ice crystals and sit at the top of the layer of the atmosphere called the Troposphere where all the weather takes place. Cirrus is usually a sign that a frontal system containing strong winds is on the way or they can be found in the anvil of a Cumulonimbus. These clouds are known also as 'Mares' Tales' and are found around 4-10 miles up from sea level.

Cirrostratus

Cirrostratus are sheets of stratus like formation high in the sky. These are not particularly a sign of bad weather to follow. The sheet is made mostly of ice and is often seen in winter following on from periods of snow where the sun is visible through the cloud. Sometimes these can produce isolated snow flurries in winter. Again these clouds are 4-10 miles up from sea level.

Cirrocumulus

Cirrocumulus are uniformed sheets of cumulo-form cloud usually made of ice. These clouds indicate higher level instability particularly in summer and can be a sign of a coming thunderstorm. In winter these clouds often precede snow showers and can again give their own flurries if it is cold enough. These clouds are usually made of ice. The clouds are also known as 'Mackeral Sky' due to the fish-scale apperance they take on. These clouds are usually found around 4-5 miles up from sea level.

Altocumulus

Altocumulus are patches of cloud usually found in a uniformed formation and these clouds are usually made of ice or water droplets. These are very good sign of mid-high level instability and can sometimes tell of a thunderstorm or heavy shower on its way. In the winter these clouds can tell of storms and snow following but these clouds do not give any precipitation. These cloud are usually found 2-6 miles above sea level.

Altostratus

A sign that a front is on the way, these clouds can tell whether there will be periods of rain or snow and are often the cloud that precedes Nimbostratus on a warm front. These clouds are thick and they take on a sheet formation of water droplets or ice crystals. These clouds can even produce hours of snow themselves under the right conditions. These cloud again are found about 2-6 miles above sea level

Cumulonimbus

These clouds can tower as high as mount everest and are famous for their thunderstorms. A Cumulonimbus consists of a Towering Cumulus and an anvil of cirrus on the top. Although the bases of these clouds are less than 2.5 miles above sea level they can extend about 10 miles into the higher reaches of the Troposhere. The clouds are made of ice crystals and water droplets and give heavy rainfall and hail and sometimes snow associated with a cold front.

Cumulus

These clouds are usually fluffy fair-weather clouds built up by convection but enough sunlight can transform them into Towering Cumulus which can give torrential afternoon downpours. These clouds are made of water droplets though a Towering Cumulus can have ice crystals as the main feature at the top. These are mainly a shower cloud and can give showers of rain or snow. These clouds again form less than 2 miles above sea level.

Nimbostratus

These are deep layers of stratus usually associated with warm or occluded fronts. These clouds give precipitation of rain or snow and sometimes even hail and have been known to produce lightning. These clouds are slow moving and have a shallow temperature gradient associated with the warm front and usually indicate stable air is on the way. These clouds are made of water droplets and are found around about 2 miles above dea level.

Stratus

These clouds are low level, uniformed sheets of thick grey cloud. These clouds often appear with weak fronts and are usually a sign of stable air. Such clouds produce drizzle or light rain and when they hit ground level they are known as fog. These clouds are particularly associated with High Pressure areas of the Atlantic in the winter and summer where the land is cool and the sea is warm. These clouds are made from water droplets and form below 2 miles above sea level.

Other Clouds

They are the cloud types that are the mechanics of our atmosphere but there are other clouds including Mammatus which are found under Cumulonimbus anvils during a death of a severe thunderstorm. Also Pileus clouds which are a good indication of a strong shear these are wispy clouds that over ride Towering Cumulus clouds. Of course the noctilucent clouds that produce eerie shape and colours that are crafted by split colours from the sun or other sources of light.