Download What is a Cloud?

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What is a Cloud?
A cloud is a collection of millions of tiny droplets of water or ice crystals. The droplets are so small and light that they can float in the air. A cloud forms when warm air rises and cools, and becomes saturated. When air is saturated and cools, the air can't hold as much water vapor. This causes some of the water vapor to condense on tiny pieces of dust, smoke, salt, even air pollution. At temperatures above freezing, water vapor condenses and forms tiny water droplets around each dust particle. At temperatures below freezing, water vapor changes directly to a solid to form tiny ice crystals. When billions of these droplets come together, they form a visible cloud.
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More about Clouds...
Clouds are white because they reflect all the colors in sunlight the exact same amount. When you combine all the colors in light together, you get white. When clouds get thick enough or high enough so all the light above does not make it through, they have a gray or dark look.
Clouds move with the wind. High cirrus clouds are pushed along by the jet stream, sometimes traveling at more than 100 miles­per­
hour. When clouds are part of a thunderstorm they usually travel at 30 to 40 mph.
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When is a Cloud Not a Cloud?
Fog is basically a cloud that forms near the ground. Contrails are not clouds. They are condensation trails left behind jet aircrafts. Contrails form when hot humid air from the jet exhaust mixes with cooler air around it with lower pressure. Apr 29­9:15 PM
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Types of Clouds
Clouds can easily be broken into four categories. These categories are high clouds, middle clouds, low clouds and clouds with vertical growth. Clouds are also identified by shape. Cumulus refers to a "heap" of clouds. Stratus refers to clouds that are long and streaky. Nimbus means "rain" as these types of clouds typically produce rain or storms. Cloud Group
Cloud Height
Cloud Type
High Clouds: Cirrus, Cirro­
Above 18,000 ft
Cirrus
Cirrocumulus
Cirrostratus
Middle Clouds:
Alto­
6,500­ 18,000 ft.
Altocumulus
Altostratus
Low Clouds:
Strato­, ­stratus
Up to 6,500 ft
Stratus
Stratocumulus
Nimbostratus
Vertical Clouds:
Cumulus
Cumulonimbus
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Cirrus
Cirrus clouds are thin, white wispy clouds made of ice crystals and blown by high winds into long streamers. They usually predict fair to pleasant weather, but, they usually indicate a change in the weather will occur within 24 hours. Apr 29­9:15 PM
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Cirrocumulus
Cirrostratus
Cirrostratus clouds are thin, sheet­like, high clouds that can cover the entire sky. Cirrostratus clouds usually come 12­24 hours before a rain or snow storm. Cirrocumulus clouds appear as small, rounded white puffs that appear in long rows or look like ripples. Mostly these mean fair weather for the near future. However, in the tropics, these clouds may indicate an approaching tropical storm or hurricane (depending on the season).
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Altostratus
Altocumulus
Altostratus clouds are gray mid Altocumulus clouds are mid level clouds that usually cover level clouds that appear as puffy the entire sky. In the thinner masses, usually in groups. areas of the clouds, the sun may be dimly visible as a round disk. If seen on a warm, humid morning, be prepared to see Altostratus clouds often appear thunderstorms late in the a few hours ahead of a warm afternoon. front that brings precipitation. Apr 29­9:15 PM
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Stratus
Stratus clouds are uniform grayish clouds that often cover the entire sky. They look like fog that doesn't reach the ground. Light mist or drizzle sometimes falls out of these clouds.
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Nimbostratus
Stratocumulus
Stratocumulus clouds are low, puffy and gray. Most form in rows with blue sky visible in between them. Stratocumulus clouds usually don't rain, but they can turn into nimbostratus clouds. Nimbostratus clouds form a dark gray, wet looking cloudy layer. They often produce continuously falling light to moderate rain or snow that can fall for long periods. Apr 29­9:15 PM
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Cumulus
Cumulus clouds are white, puffy clouds that look like pieces of floating cotton with a flat base and puffy, rounded towers.
Cumulus clouds are often called "fair­weather clouds." But, if they start to grow vertically, they may indicate a coming thunderstorm.
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Cumulonimbus
Cumulonimbus clouds are very tall thunderstorm clouds. High winds can flatten the top of the cloud into an anvil­like shape. Cumulonimbus clouds are associated with heavy rain, snow, hail, lightning and even tornadoes. Apr 29­9:15 PM
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