All you need to know about 4 types of clouds

Different varieties and types of clouds are categorized according to their shapes and height in the troposphere. In this article, Interesting Engineering (IE) discusses the various types of clouds, including how they differ. 

Categories of Clouds

Did you know that an actual cloud atlas exists? That’s right, the World Meteorological Organization (WMO) maintains one which categorizes clouds into genera, species, and varieties. Most clouds can be distinguished based on how high they hover in the troposphere. 

In case you don’t know what the troposphere is, it’s the lowest part of the atmosphere, rising from the Earth’s surface to an average height of 13 kilometers. 

While alternative methods for categorizing clouds according to their distinct characteristics exist, IE summarizes four types of clouds, encompassing more than 10 typical forms of clouds. 

The elements of this classification system are described using the following cloud roots: Cirro-: curl of hair, high; Alto-: mid; Strato-: a layer; Nimbo-: rain, or precipitation; Cumulo-: a heap.

High clouds 

Clouds occurring at or above an altitude of 20,000 feet are classified as high clouds. The temperatures at these heights are below freezing point (less than zero degrees celsius). As a result, the water moisture in high clouds is in the form of supercooled water droplets or ice crystals.

High clouds are divided into three sub-types:

Cirrus

Cirrus clouds are thin, feathery, wispy, and hair-like. These clouds are mostly comprised of ice crystals. The wind currents twist and spread these ice crystals into delicate strands. Due to this, when you look at these clouds from below, they appear to have no structure.

Cirrostratus

Cirrostratus clouds are delicate, white clouds. These clouds appear like a veil covering the entire sky. These clouds are common in winter, often predicting rain or snow within 24 hours. They often produce a halo around the Sun or the Moon, making the environment somewhat ‘mysterious-looking.’ They form as a result of slowly rising air, and are usually generated at the forefront of frontal weather systems.

Cirrocumulus

Cirrocumulus clouds are sheet-like clouds that are thin, white, and sometimes patchy. These clouds contain supercooled water droplets and may appear full of ripples. They can also look like they’re made of small grains. For people living in tropical regions, these clouds can predict an approaching hurricane.

Mid-level clouds

Mid-level clouds form between 6,500 and 20,000 feet. These clouds are often flat and layered because the air at these altitudes doesn’t move vertically. 

These clouds may be made of liquid water droplets, ice crystals, or a combination of the two, including supercooled droplets (i.e., liquid droplets whose temperatures are below freezing). This depends on the altitude, the season, and the vertical temperature structure they form in.

As such, the temperatures for mid-level clouds are between 0 and -40. They include the following types: 

Altocumulus

Altocumulus clouds appear lower than cirrus clouds but are still relatively higher than low-level clouds. These clouds are usually made of liquid water but may contain some ice crystals. They form in settled weather and are not generally responsible for producing rain. They come in different forms but mostly appear like rounded masses. 

They may form from the breakup of altostratus, the lifting of moist air pockets, or atmospheric waves over mountains.

These clouds often have multiple patchy gray or white layers that look like small rows of ‘fluffy’ ripples.

Altostratus

Altostratus clouds are sheet-like clouds that cover the sky, but the sheet is patchy with thin sections to reveal the sun. 

Unlike cirrostratus clouds, altostratus clouds don’t produce a halo around the sun or moon, although they may contribute to the formation of optical effects such as coronas and iridescence. These clouds look gray or blue-gray. They often spread over thousands of square miles, and can predict light rain or snow.

While they do not produce heavy rain, they can morph into nimbostratus clouds (below), leading to rain or snow. They usually form when a layer of cirrostratus cloud descends from a higher level.

Nimbostratus

Nimbostratus clouds are thick, dark, gray-layered clouds with few distinct features. These clouds often create a gloomy aura and can indicate the onset of heavy rain or snow. Their thickness blocks out sunlight. 

They are often associated with frontal systems and may form from the deepening and thickening of altostratus cloud, often along warm or occluded fronts.

Low clouds 

Low clouds contain liquid water droplets and occur at less than 6,500 feet. In some cases, they may consist of supercooled droplets, but during cold winter storms, they are composed of ice crystals and snow.

Low clouds are of the following types:

Cumulus

Cumulus clouds are the classic clouds. They look like white, fluffy cotton balls in the sky that appear dense and detached. The part of cumulus clouds lit by sunlight is bright white, while their bases are a uniform dark color. These clouds tend to look ‘heavenly’ during sunsets with their varying shapes and sizes. They are formed through convection as air heats at the surface and rises, then cools, causing water vapor to condense to produce the cloud.

Stratus

Stratus clouds are thin, gray or white layers covering the entire sky. These super-thin clouds don’t produce much rain or snow yet still manage to keep the weather ‘gloomy-looking.’ 

You can see their outline if the sun is out. In some cases, they may produce light drizzle or snow. These clouds appear to be fog in hills and mountains. They form in calm, stable conditions when gentle breezes raise cool, moist air over colder land or ocean surfaces.

Cumulonimbus

Cumulonimbus clouds are dense and heavy. These clouds appear on hot days when warm and wet air rises high in the sky. They look like tall mountains or vertical towers when observed from far away. 

If these clouds are observed during a storm, they are referred to as thunderheads. In this case, they can produce lightning, tornadoes, hail, and heavy rain.

Stratocumulus

Low-lying clusters or patches of cloud called stratocumulus clouds range in color from dazzling white to dark grey. They are the most prevalent clouds on Earth and may be identified by their distinct bases, some of which are frequently darker than others. 

Although there are typically spaces between them (honeycomb-looking), they can also be connected. Additionally, stratocumulus clouds usually form when a stratus cloud layer breaks up. 

They are signs of changing weather. Although they can be found in many kinds of weather, from dry settled weather to more rainy conditions, stratocumulus clouds are frequently not the cause of the problem.

Contrary to popular belief, it is uncommon to experience anything from a stratocumulus cloud other than the tiniest drizzle.

Special clouds

The following clouds only occur under ‘special’ circumstances. They usually appear as a result of human activity or localized conditions.

Contrails

Aircraft condensation trails, or contrails, are made by high-flying airplanes. These clouds appear high in the troposphere, where aircraft and jets tend to fly. They are a unique homogenitus (human-induced) cloud made with water droplets condensed from the water vapor in the jet engine’s exhaust. 

These clouds can provide information about the moisture layers in the sky.

Mammatus

Mammatus clouds are often seen before a thunderstorm. These clouds are basically cirrus, altocumulus, or cumulonimbus clouds with pouch-like protrusions at the bottom. 

These pouches form when cold air in the cloud sinks toward the Earth. This is a unique trait because most other clouds form when air rises, while mammatus clouds form when air sinks.

Orographic

Orographic clouds resemble mountains or hills in shape. They force the air to move around or over them. Sometimes, these clouds form due to sea breeze or due to the lifting of air over geographic features, like mountains, and look like lines where two air masses meet. These clouds often predict afternoon thunderstorms.

Lenticular

Lenticular clouds are lentil or almond-shaped type of orographic cloud that forms in the lower to middle troposphere. These clouds resemble flying saucers or spaceships and often form when the wind blows over a large object, like a mountain. On the ground, they can signal very strong winds in one place, even though the air only a few hundred feet or meters away is still.

They are technically a variant of stratocumulus, altocumulus, or cirrocumulus clouds.

Why are clouds important?

The energy balance, climate, and weather of Earth are all significantly influenced by clouds. The primary factor controlling the planet’s average temperature is clouds.

Because they reflect some of the Sun’s energy, also known as solar energy or solar radiation, back to space, some clouds also aid in cooling.

Other clouds also contribute to warming by acting as a blanket and trapping part of the thermal energy or longwave radiation that the Earth’s surface and lower atmosphere emit.

The energy of the Sun is also dispersed throughout the surface of the Earth via cloud structures. Storms move across the surface of the earth, carrying energy from warm regions close to the equator to cold regions close to the poles.

Even little changes in cloud cover or location have the potential to have a greater impact on climate change than anticipated changes brought on by greenhouse gases, man-made aerosols, or other global warming-related causes. 

Final thoughts

Clouds are interesting natural phenomena that spread across the entire sky. Every day we see clouds varying in shape, color, size, and density. Knowing this and taking all the above information into consideration, why not try to classify a cloud in real-time the next time you’re out?