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What is the most common cloud type around the world? why?
Question Date: 1999-06-08
Answer 1:

I think if I tell you a little bit more about clouds then you can think about an answer to your question yourself:

Clouds are usually the most obvious feature of the sky. They both reflect weather patterns and play a role in what the weather does. In addition to their obvious role as sources of precipitation, clouds also can affect the temperatures of the places below them. Clouds not only block incoming sunlight during the day, which cools the air, but they can also block outgoing radiation from the Earth. Many unanswered questions about Earth's climate revolve around the roles of clouds. Clouds also create some patterns of light in the sky such as halos.

Here are several examples of cloud names.
Fog is a cloud on the ground.
Stratus clouds are a uniform gray and usually cover most of the sky.
Cirrus clouds are thin and high in the sky.
Cumulus clouds are lumpy and can stretch high into the sky.
Mammatus clouds have pouches that hang down.

Fog forms near the ground when water vapor condenses into tiny liquid water droplets that remain suspended in the air. It is accurate to describe fog as a cloud near the ground. Fog is usually associated with fair and calm weather, but the reduced visibility can close airports and cause numerous travel headaches. Many different processes can lead to the formation of fog, but the main criteria for fog formation is saturated air. The two ways air can become saturated are cooling the air to its dewpoint temperature or evaporating moisture into the air and increasing its water vapor content.

Stratus clouds are uniform gray clouds that usually cover the entire sky. They can form when very weak, upward vertical air currents lift a thin layer of air high enough to initiate condensation. Stratus clouds also form when a layer of air is cooled from below to its dewpoint temperature and water vapor condenses into liquid droplets. Stratus clouds look like a layer of fog that never reaches the ground. In fact, fog that "lifts" off the ground forms a layer of low stratus clouds. Precipitation rarely falls from true stratus clouds since the upward vertical motion needed for precipitation is very weak, but light mist and drizzle can sometimes accompany stratus clouds.

Cirrus clouds are thin, wispy clouds that usually form above 18,000 feet. These clouds are blown by strong westerly winds aloft into streamers known as "mares' tails" Cirrus clouds generally move from west to east across the sky and usually "point" to fair weather. Cirrus clouds form when water vapor undergoes deposition and forms ice crystals. Cirrus clouds are thin because they form in the higher levels of the atmosphere where little water vapor is present.

Cumulus clouds form as water vapor condenses in strong, upward air currents above the earth's surface. These clouds usually have flat bases and lumpy tops. Cumulus clouds are usually very isolated with large areas of blue sky in between the clouds. Most cumulus clouds form below 6,000 feet and are relatively thin and associated with fair weather. However, when the atmosphere becomes unstable and very strong, upward air currents form, cumulus clouds can grow into cumulus congestus, or towering cumulus. If the atmosphere is unstable enough, cumulonimbus clouds, better known as thunderstorms, form. Cumulus congestus and cumulonimbus clouds can tower from below 6,000 feet to greater than 50,000 feet.

Mammatus clouds often form on the underside of cumulonimbus clouds, but are sometimes seen underneath other clouds as well. They can appear threatening, but the sinking air required to make these clouds actually indicates weakening of the storm associated with them. No matter how threatening, these spectacles of nature are actually a blessing in a quite impressive disguise

Here is a great web site if you want to know more:

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