Vocabulary #3: Types of clouds

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As a pilot who travels around the world you must be familiar with the meteorology. You certainly know how bad weather conditions can influence a flight and lead to accidents with fatalities. The subject is vast so let’s start with the clouds.

Cloud classification

Clouds are constantly changing and there are an infinite variety of shapes. They can be classified according to the heights where they form.

Cloud level (feet)Cloud types
High clouds (CH)
Base usually 20,000 ft or above
• Cirrus
• Cirrocumulus
• Cirrostratus
Medium clouds (CM)
Base usually between 6,500 and 20,000 ft
• Altocumulus
• Altostratus
• Nimbostratus
Low clouds (CL)
Base usually below 6,500 ft
• Stratocumulus
• Stratus
• Cumulus
• Cumulonimbus

By Valentin de Bruyn / Coton (Own work) [<a href="http://creativecommons.org/licenses/by-sa/3.0">CC BY-SA 3.0</a> or <a href="http://www.gnu.org/copyleft/fdl.html">GFDL</a>], <a href="http://commons.wikimedia.org/wiki/File%3ACloud_types_en.svg">via Wikimedia Commons</a>

By Valentin de Bruyn / Coton (Own work) [CC BY-SA 3.0 or GFDL], via Wikimedia Commons

The names of clouds are a combination of some Latin prefixes and suffixes. If you know their meanings, that can help you to remember the different kinds of clouds and what their names imply.
Prefixes/SuffixesMeaning
Stratus/stratoflat, layered and smooth
Cumulus/cumuloheaped up, puffy, like a cauliflower
Cirrus/cirrohigh up, wispy, curly or fibrous
Altomedium level
Nimbus/nimborain-bearing cloud

Description of some clouds

Cirrus clouds are characterized by wispy strands that have various shapes. They are made of crystal ice because where they form the air always freezes. They are generally see-through. These clouds indicate a change in the weather that will lead to steady rain. They produce rain, but they evaporate before reaching the ground. Cirrus clouds are the fastest moving clouds.

Altocumulus clouds are in the form of layers of cotton-wool balls. The precipitation from altocumulus rarely reaches the ground. Altocumulus clouds may tower and change into altocumulus castellanus clouds that indicate a thunderstorm is coming.

Nimbostratus clouds are opaque and have a vaporous and non-well-defined shape. They are so thick that they often block the sun. They are a sign of steady precipitation, but they are not associated with thunderstorm. They form from altostratus clouds which descend in lower altitude and thicken.

Stratocumulus clouds are the most common clouds in the world. They are same in appearance to altocumulus. Their colour can change from with to dark grey. They sometimes produce rain or snow, but it’s quite uncommon. These clouds are formed either through the spreading and joining together of cumulus clouds, or by the breaking up of stratus clouds.

Stratus clouds are layer clouds. They don’t have a well-defined shape, they are an overcast sky. They are essentially above-ground fog formed through the lifting of morning fog. They don’t indicate much meteorological activity.

Cumulus clouds often have a flattish base and cauliflower upper surface. They are often called fair-weather clouds because they do not bring rain or snow. However, they can give raise to other types of clouds and change into cumulonimbus. They are really useful for glider pilots as they can indicate rising air drafts.

Cumulonimbus clouds are the largest and the most powerful of all clouds. They are towering vertical clouds often characterized by an anvil’s shape. When they develop vertically, they cover all the three clouds regions; they can form up to 60,000 feet. They can provoke thunderstorms and lightning and in some cases tornadoes. These clouds are undoubtedly the most dangerous clouds for pilots. Pilots must not go through a cumulonimbus because the air draughts coming up and down in it can easily flip their planes over.

You probably know that when you are flying, your aircraft sometimes leaves a kind of track after it. But did you know it has a name? These tracks are called contrails. They are formed by the air vapour coming of the aircraft. They appear when the air is cold and moist enough. They are a clear indication of the human activity up in the sky.

There are still a great number of clouds that are more uncommon.

Mammatus clouds also known as breast clouds are lumpy lobes at the base of a cloud layer. They often appear after a storm or indicate that heavy showers are falling some distance away.

Noctilucent clouds are the highest clouds in the Earth’s atmosphere. They form at around 250,000 feet. They are very rare and only form in summer at latitudes between 50° and 70° north and south of the equator. These clouds are light blue and they are so high that they catch the sunlight even if the rest of the sky is dark.

Lenticular clouds also called lenticularis are lens-shaped clouds. They can form at all of the three clouds levels. They were often confused with UFOs. Pilots try to avoid flying through these clouds due to the turbulence above them.

References

BBC ONE: Cloud spotting guide
Livescience: Types of clouds
Met Office: Cloud names and classifications
Wikipedia : List of cloud types
Macmillan Dictionary
Cambridge Dictionaries Online

Let’s see if you can answer some questions about this article.
You can choose more than one answer.

Match the words with the right definitions.