Atmosphere And Weather

How Clouds Form

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"How Clouds Form"
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Put very simply: Clouds are formed from condensed water or ice. This occurs when the rising and expanding air cools enough to allow a proportion of the water vapour molecules to "stick" together, which then condense to form visible cloud droplets or ice crystals.

The result is one of the most beautiful and awe inspiring creations of nature, which come in a variety of shapes and sizes, and help us to gain a good idea of prevailing weather conditions.

After the ice or water droplets have condensed, they smash into each other until the cloud is so large that it becomes too heavy and drops half of its moisture as snow or rain, whilst the other half reverts back into water vapour.

They hang up in the sky like huge puffs of cotton wool, but in fact the reason why they float is because when the air is heated by the sun, it always rises, and as it does, it then cools, reaching saturation point and thus condensing which forms the cloud. The cloud will float in the air just as long as its outside temperature is cooler around it.

Clouds are white because they directly reflect back the light from the sun...If they go a gray color, that is because the light cannot penetrate the whole cloud, especially if there is more cloud in proximity, or it has climbed higher.

Clouds are moved by the wind and can sometimes reach speeds of up to 100 miles an hour!

Cloud Types

Cirrus clouds, often called mare's tails, appear as wispy white clouds blown into long streamers by the wind. They predict fair weather.

Cirrostratus clouds are very fine, sheer clouds that can cover the whole sky. They indicate a change in the weather within 12 to 24 hours which will bring rain or snow.

Cirrocumulus clouds are small, rounded white puffs that appear in long row and can be likened to fish scales. Usually seen in the winter, they indicate fair, but cold weather. In tropical regions, they could signal an approaching hurricane.

Altostratus clouds are gray or blue-gray in color and are often formed before a storm occurs and bring continuous snow or rain. They usually cover the whole sky with a thin mantle, with the sun showing dimly behind it.

Altocumulus clouds are recognizable by their puffy gray masses and often form in clumps. They foretell late afternoon thunderstorms after a warm morning.

Stratus clouds are garish clouds that cover the entire sky. Light mist or drizzle results from this type of cloud.

Stratocumulus clouds will form in low, puffy rows with patches of blue sky between them. They rarely give out rain but can transform into nimbostratus clouds.

Nimbostratus clouds look like dark gray, cloudy layers that produce light to moderate precipitation.

Cumulus clouds are the ones that look like cotton wool floating in the air. Associated with fair weather, these flat based clouded with their amazing rounded towers can often give a "cauliflower" type shape. If they rise too far they can then develop into huge cumulonimbus clouds, which are known as thunderstorm clouds.

Cumulonimbus clouds are shaped by high winds and will often have an anvil shape. These clouds are linked to heavy rain, snow, hail, lightening and tornadoes.

The next time that you look up into the air and idly pick out imaginary figures and fairy castles in the air, it is a sobering thought that all that those beautiful shapes are simply composed of water vapour and warm air. References:


Clouds. Accessed 11/11/2008

Clouds. Accesses 11/11/2008

More about this author: Jane Allyson

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