The World Meteorological Organization recognizes more than a hundred different types of clouds. However, they can be categorized into 10 main types based on their overall shape and the altitude where they form.
Clouds are classified and named using a system known as Luke Howard’s nomenclature, named after the British chemist who proposed it in 1802. This method sorts clouds into five groups based on their convective activity and then further classifies them according to three altitude levels:
- Low-Level: Clouds below 1,981 meters
- Mid-level: Clouds between 1,981 and 6,096 meters
- High-level: Clouds forming above 6,096 meters from sea level
It’s important to note that each cloud type can also be broken down into species and then further into varieties.
We have mentioned 10 different types of clouds (based on their altitude levels) that will give you more insights into the language of the skies, helping you interpret the weather and appreciate the celestial spectacle above.
Did you know?
On average, nearly 67% of the Earth’s surface is covered by clouds at any given time. These clouds vary greatly in size, from small, wispy cirrus clouds that stretch across the sky to massive cumulonimbus clouds that can tower over 10 miles high.
Table of Contents
Low-Level Clouds
10. Stratus
Symbol: St
Stratus clouds are mostly flat, featureless, and grayish in appearance. They form slightly above the ground at lower altitudes either due to subsiding colder air or the lifting of morning fog over a region. They are also known as “high fog” clouds.
What they indicate:
Stratus cloud formation typically suggests prolonged cloud cover with light rain and occasional snowfall. These clouds are more persistent in anticyclonic conditions. While light rain may occur, this cloud type does not indicate significant meteorological activity.
9. Cumulus
Cumulus clouds from above
Symbol: Cu
We are all familiar with cumulus clouds from our younger days. The puffy or fluffy appearance of cumulus clouds was often what we thought of when we heard the word ‘cloud,’ right?
Cumulus clouds typically form on clear days below 2,000 meters altitude. They have well-defined edges and usually appear in clusters or grids.
What they indicate:
While cumulus clouds are not strongly associated with precipitation, weather factors such as moisture and temperature gradient can cause them to quickly transform into cumulonimbus clouds, resulting in heavy rain and thunderstorms.
8. Stratocumulus
An enhanced image of Stratocumulus cloud | Image Courtesy: Arun Kulshreshtha
Symbol: Sc
Stratocumulus clouds are basically a larger and less smooth version of the cumulus clouds. They usually occur in large patches below 2,000 m altitude. Stratocumulus is fairly common over the subtropical and polar regions.
What they indicate:
Stratocumulus clouds often result in light rain or snowfall only. The interesting thing, however, is that they almost always appear before or after extreme weather conditions such as thunderstorms and gust fronts.
Furthermore, these clouds can create Crepuscular rays, which are sunbeams shining through openings in the clouds during the day. They can also cause the corona effect sometimes seen around the moon at night.
7. Cumulonimbus
Anvil-topped Cumulonimbus cloud
Symbol: Cb
Cumulonimbus, also known as towering vertical cumulonimbus, are large and dense clouds shaped by powerful upward rising air currents. Cumulonimbus clouds are much like cumulus clouds from which they actually originate, except that they form a towering figure.
A typical cumulonimbus cloud can span from low- to mid-altitude and, in extreme cases, high-altitude levels. These clouds typically have an anvil-like upper layer and a dark base.
What they indicate:
Cumulonimbus clouds are a telltale sign of imminent extreme weather conditions. They can lead to severe lightning, flash flooding, and even tornadoes.
Mid-Level Clouds
6. Nimbostratus
Nimbostratus clouds
Symbol: Ns
Nimbostratus presents itself as a dark and mostly shapeless cloud that originates in mid-altitudes and extends vertically to low and high levels. They can be found anywhere below 3,000 meters altitude.
What they indicate:
Nimbostratus clouds are a sign of possible moderate but persistent rain brought down by a warm front. Unlike cumulonimbus clouds, they usually do not produce thunderstorms, but because of the unstable conditions of warm fronts, thunderstorms are still possible.
5. Altostratus
Altostratus clouds over Hong Kong
Symbol: As
Altostratus clouds are characterized by uniform, grayish layers mainly made up of ice crystals, appearing featureless. They have a lighter shade compared to nimbostratus clouds.
These clouds form when water vapor condenses from a large, stable air mass as it reaches mid-altitudes. They often cover a wide area of the sky, and their thickness can vary.
What they indicate:
Altostratus clouds can bring rain, especially when they thicken. Initially, it may start as light showers and then progress to moderate rain. When the rain becomes more consistent, they are reclassified as nimbostratus clouds.
4. Altocumulus
Partially illuminated Altocumulus clouds | Wikimedia Commons
Symbol: Ac
Altocumulus clouds are perhaps the most common cloud type found in the mid-latitudes. They are distinguished by closely placed grey or white patches.
It can be challenging to distinguish altocumulus from stratocumulus clouds since they look very similar, but altocumulus clouds have much smaller individual mounds.
What they indicate:
Altocumulus clouds are usually followed by thunderstorms, even though they are not associated with rain. The presence of altocumulus castellanus, which are towering vertical altocumulus clouds, indicates turbulence in the mid-atmosphere.
Because of their instability, altocumulus clouds are recognized as one of the most potentially dangerous clouds for aviation.
High-Level Clouds
3. Cirrus
A subform of cirrus clouds
Symbol: Ci
Cirrus clouds can be easily recognized by their thin, feather-like strands. They usually form above 5,500 meters and, in extreme cases, at 13,000 meters above sea level.
Unlike other clouds that are primarily composed of water vapor, cirrus clouds are made up of thin ice crystals. At altitudes above 5,500 meters, water vapor undergoes deposition, forming these ice crystals.
Cirrus clouds play a significant role in the Earth’s greenhouse effect. While they reflect only a small portion of incoming solar radiation, they block about half of the escaping infrared radiation from the planet’s atmosphere.
What they indicate:
An extensive cover of cirrus clouds is enough to indicate turbulence in the upper atmosphere and a possible cyclone formation over the region.
In the late 1800s, meteorologists monitored these clouds to predict hurricanes. Benito Viñes, president of Belén College in Havana, Cuba, developed a similar hurricane forecasting system in 1870.
2. Cirrostratus
Cirrostratus clouds featuring a moon halo | Image Courtesy: Sean Mack
Symbol: Cs
Cirrostratus clouds are thin, uniform, and translucent, making them quite challenging to identify. These clouds usually feature ring-like halos surrounding the Sun and/or the moon. The halo(s) is caused by the refraction of light on the ice crystals within the cloud.
Along with the Storm Ring, refraction of light by cirrostratus clouds can give the sun the appearance of six distinct rays around it. This phenomenon precedes storms, and undoubtedly would’ve inspired the Wheel of Taranis, the Slavic Perunika, and perhaps even the Hagal rune. ᚼ pic.twitter.com/K7IqPIAil1
— Sagnamaðr Stark (@Sagnamadr) February 13, 2024
What they indicate:
Generally, cirrostratus clouds signal an approaching warm front over the region and bring precipitation along with it. These clouds, when formed over the polar regions, can carry nitric acid.
1. Cirrocumulus
Image Courtesy: Tony Jin
Symbol: Cc
Cirrocumulus are small and patchy white clouds that usually appear between 4,800 meters to 11,800 meters above sea level.
Unlike the two other main high-altitude cloud types, namely Cirrostratus and Cirrus, Cirrocumulus clouds carry small amounts of supercooled liquid water rather than ice.
Each individual cloud mound, known as a cloudlet, in cirrocumulus clouds is much smaller than those in altocumulus and stratocumulus clouds.
What they indicate:
Cirrocumulus clouds usually do not lead to precipitation. However, on rare occasions when they appear with cirrus or cirrostratus clouds, there is a possibility of rain.
A fallstreak hole also called a hole punch cloud is a large circular or elliptical gap that can appear in cirrocumulus or altocumulus clouds. It is often attributed to UFOs due to its rarity and unusual appearance. pic.twitter.com/1W3H8Np2Kh
— Intriguing and unexpected content! (@WriteEditPJ) February 13, 2024
If you’re interested in learning more about clouds, you can check out the WMO’s International Cloud Atlas.
Read: 6 Different Types of Volcanoes
More To Know
What is the difference between fog and clouds?
Fog is a type of cloud that forms near the ground, typically reducing the visibility at or near the Earth’s surface. Clouds, on the other hand, form at different altitudes in the atmosphere.
| Fog | Cloud |
| Forms near the ground, consisting of tiny water droplets or ice crystals suspended in the air | Visible masses of condensed water vapor or ice crystals suspended in the air |
| Forms when the air near the ground becomes saturated with moisture | Forms when moist air rises and cools |
| Reduces visibility, making it difficult to see distant objects | Can be seen from above or below, depending on the altitude |
| Common during cool and clear nights or in regions with high humidity | Occur under different weather conditions, including clear or stormy weather |
| Dissipates as the ground warms and the air mixes, or as wind disperses it | Dissipate as temperatures rise or as the atmosphere becomes drier or the wind disperses them |
| Can disrupt transportation | Can affect aviation, weather patterns, and climate |
Why do clouds have different shapes?
Clouds have different shapes primarily due to variations in atmospheric conditions, such as humidity, air temperatures, and wind patterns. For example, the movement of air masses and turbulence can sculpt clouds into different forms, like the billowing shapes of cumulus clouds or the delicate wisps of cirrus clouds.
Furthermore, factors like topography and the stability of the atmosphere can influence cloud formation, resulting in myriad shapes and patterns that contribute to the ever-changing spectacle of the sky.
Some Rare or Unique Cloud Formations
- Lenticular Clouds are lens-shaped clouds that typically form near mountain
- Mammatus Clouds are characterized by their bubble-like or pouch-like formations
- Arcus Clouds are often associated with gusty winds and heavy rain
- Kelvin-Helmholtz Clouds form when there is a large difference in wind speed between two layers of air
These unusual clouds make the sky even more interesting and beautiful, captivating observers with their different shapes and features, and leaving them in awe.
Can clouds be artificially created or modified?
Yes. clouds can be artificially created or altered through a process called cloud-seeding. This process involves introducing certain substances into clouds to increase precipitation or suppress hail formation.
The most common substances used for cloud seeding are silver iodide, sodium chloride, and potassium iodide. They act as nuclei around which water droplets can form, thereby increasing the likelihood of precipitation.
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