Cloud Names











Curl of hair



Violent rain

Rain cloud

All Cloud Types
The various cloud types are depicted above.

have a more moderate temperature range—the difference between daily high and low temperature—than cloudless days.

Almost all clouds are found in the troposphere. They are classified by their appearance into 4 main groups, as shown in the table on page 48. These 4 main groups contain 10 cloud types, classified by appearance and height above the ground.

High clouds reside at greater than 20,000 feet (6,100 m). They form where air is frigid and there is little water vapor; hence, they are thin and composed entirely of ice crystals. White, feathery cirrus clouds are the most common cloud type at this altitude. They appear as long, windblown streamers called mares' tails. Cirrus clouds may warn of an approaching storm. Cirrocumulus clouds are small, white puffs found in lines rippling across the sky. Sheetlike cirrostratus clouds are white and thin. They bend the incoming rays of the Sun or light from the Moon, creating a halo around them. Thicker cirrostratus clouds indicate rain or snow within the next 24 hours.

Middle clouds, located between 6,500 and 23,000 feet (2,000 and 7,000 m), are composed of water vapor or ice crystals. Altocumulus clouds are gray, puffy blobs seen as bands rolling across the sky; they often herald late afternoon thunderstorms. Altostratus clouds are thick and broad and precede storms that bring widespread, nearly nonstop precipitation.

Low clouds form below 6,500 feet (2,000 m). They are composed of water droplets and contain some ice and snow in very cold weather. Stratus clouds usually cover the entire sky but rarely produce rain. Thick and dark nimbostratus clouds drop light to moderate rain or snow. Usually, stratocumulus clouds form as lines of fairly large, rounded clumps, ranging from white to gray.

The fourth group of clouds develops vertically more than horizontally. Cumulus clouds are white puffs with a flat base and a cauliflower-like head. Cumulus clouds grow as condensing

What Causes Cumulonimbus Clouds

Ominous clouds at a weather front. (NOAA Photo Library, NOAA Central Library; OAR/ERL/ National Severe Storms Laboratory)

water vapor creates vertical air currents. If their vertical currents strengthen, cumulus clouds grow into towering cumulonimbus clouds, the dramatic clouds of thunderstorms that are accompanied by rain, snow, hail, and lightning.

The stratosphere is too dry for cloud formation except during extremely chilly polar winters. At that time, polar stratospheric clouds (PSCs) form at very high altitudes, about 70,000 feet (21,000 m). Composed of water and nitric acid, these iridescent clouds are essential for breaking down chlorine-containing compounds, such as CFCs, in the stratosphere. Even higher in the polar stratosphere are noctilucent clouds, which are composed of tiny ice crystals and may form from the breakdown of methane gas.

For air at any humidity level, there is a temperature below which water vapor will begin to condense into liquid water. This temperature is called the dew point. Since air cools as it rises and cool air holds less moisture than warm air, rising air will reach its dew point at a particular altitude. This altitude is known as its condensation level, which depends on the air's temperature and humidity. The flat undersides of many clouds reveal the location of the condensation level for that air. If rising air continues to chill, the water droplets may freeze into ice.

Clouds form in the three different ways listed below. All involve the rising of warm air.

© Warm air rising from the ground exceeds its dew point, creating a cumulus cloud. As the rising air cools, it moves away from the center of the cloud then sinks back down to the ground, creating a convection cell. If the air above the condensation level is stable, the cloud will be small. If the air continues to rise, the cloud will mushroom into a cumulonimbus cloud. If the cloud reaches the stratosphere, it can no longer grow upward and instead grows outward, creating a flat, anvil-shaped summit.

© Warm air is pushed upward at a mountain or mountain range. If the humidity is high enough, clouds form and may precipitate. As the air descends on the other side of the mountains, it warms, causing the rain shadow effect.

© Warm air is wedged upward by a mass of cold air. This forms a front, which may be characterized by clouds that cover hundreds or thousands of square miles.

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  • Natsnet
    How Are Clouds Classified?
    6 years ago
  • renzo
    What are the different couldtypes?
    6 years ago
  • Haben
    What are the 4 kinds of clouds cloud types?
    6 years ago
  • frank
    What are the names and pictures of clouds?
    5 years ago
  • jennifer harrison
    What agency names rain cloud types?
    1 year ago

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