What are clouds: types and formation

What is a cloud

A cloud is a collection of water droplets or ice crystals in the atmosphere.

They can occur not only on Earth, but also on other planets or moons.

The cloud-like formations we often see floating between stars are called ‘nebulae’, which are collections of material between stars, or interstellar matter.

The Milky Way, on the other hand, is a structure formed by a collection of stars and is different from a cloud.

Clouds are formed by the condensation of water vapour in Earth’s atmosphere.

The water droplets in these clouds are mostly small, with a radius of roughly 0.02 to 0.05 millimetres. Billions of these tiny droplets come together to form what we see as a cloud.

When clouds are densely packed together, their ability to reflect sunlight is stronger, making the top part of the cloud appear brighter. On the other hand, the lower part of the cloud can appear dark grey due to light scattering.

Clouds can also change colour depending on the angle of the sunlight and the surrounding environment. Clouds are also effective absorbers of infrared light.

Clouds are also one of the main causes of many weather phenomena.

When water droplets or ice crystals grow larger in clouds and fall under the influence of gravity, precipitation events such as rain, snow, and hail occur.

Types of clouds

Clouds can be classified according to different shapes and heights.

Firstly, by shape, they are divided into cirrus, stratus, stratocumulus, and cumulus. Secondly, by height, they are divided into upper, middle, lower, and vertical clouds. The height of a cloud is judged by its base.

This classification was proposed by Luke Howard at the Asquithian Society in 1802.


Stratus clouds form in the atmosphere between 5,000 metres and 13,000 metres in altitude.

Because of the low temperatures in this region, water vapour turns into ice crystals.

However, stratus clouds can also occur at relatively low altitudes, such as 3,000 metres in the polar regions. These stratus clouds are usually faint and can sometimes be seen as transparent.

There are three main types of stratus clouds


Nicknames: hairy clouds, birdseye clouds
Appearance: white and thin, in the shape of lines, white flakes, or narrow bands. They are made up of ice crystals, the larger ones falling off at high speeds to create what looks like a tail.
Characteristic: Each part of a cirrostratus has a tail, sometimes drooping downward, that can tilt or bend irregularly with changes in wind speed and ice crystal size.


Nicknames: woolly cirrus, cotton ball cloud, swarm cloud
Form: Translucent, white veil-like clouds that can form sun or moon clusters.
Characteristic: They have cloud particles made up of ice crystals.


Nicknames: hairy clouds, scale clouds, shell clouds
Shape: Shaped like fish scales or ripples, with small cloud particles arranged in a regular pattern.
Characteristics: The cloud particles are made up of ice crystals, and iridescent clouds or rings of light can sometimes be observed.


Occurs at altitudes between 2,000 and 7,000 metres
Thin enough to faintly obscure the sun and moon, but thick enough to completely block them out
Tail or breast clouds may occur around the sun and moon


Occur at altitudes between 2,000 and 7,000 metres
White or grey, three-dimensional clouds
Iridescent clouds or rings of light may occur


Occurs at altitudes up to 2,000 metres
Low clouds that resemble fog
May produce drizzle


Approximately 500 metres at the base and 2,000 metres at the top
Large, grey, circling clouds


Occur mainly at heights of 2,000 to 7,000 metres
Rain or snow
Mainly dark grey clouds


The base of the cloud is about 2 kilometres and the top can reach up to 12 kilometres
May be accompanied by showers, hail, thunderstorms and lightning


Occur between the ground and a height of 2,000 metres
Typical cloud types on a clear day
Divided into several subtypes based on size

Creating clouds

o summarise the process of cloud formation in a nutshell, when air near the surface rises for some reason, the volume of the air expands, and as a result, the temperature of the air decreases.

When the temperature of the air drops to the dew point, the water vapour in the air condenses and turns into water droplets or ice particles, and these droplets or ice particles collect to form a cloud.

To be more specific, here are the different cases or situations where clouds form

Topographical uplift: When a part of the earth’s surface is heated more intensely by the sun, the air in that area begins to rise. For example, air encountering a mountain range is forced to rise.

Ascent by air masses: Warmer air rises above cooler air at the point where two air masses meet.

Ascent by convergence: When air converges (gathers) in an area of low pressure, it is forced to rise.

Rise by convection: When air near the surface is heated by the sun, it rises because hot air is not heavy.

When air rises in the situations described above, the volume of the air expands, and as a result, the temperature of the air decreases.

When the temperature of the air reaches the dew point, the water vapour in the air condenses and turns into water droplets or ice particles, and these droplets or ice particles collect to form clouds.

Thus, clouds form through a process that involves the rise of air near the surface, the expansion of that air’s volume, a drop in temperature, and the condensation of water vapour.

Colour of clouds

The colour of a cloud tells us what’s in it and what state it’s in.

First, when a cloud is white. This is because the water droplets in the cloud are small and reflect all of the sunlight. White clouds are usually seen in good weather.

However, if the clouds look grey or black, it means that there are lots of large water droplets or ice in them. These clouds are more likely to bring rain or snow.

Greyish-blue clouds indicate that the water droplets are getting a little bigger. When these clouds appear, large raindrops are likely to fall soon.

Light green clouds are rare, but they indicate that there are more ice particles in the cloud. These clouds have the potential for strong rain or hail.

Yellow clouds can appear when there is fire or smoke in the area. The smoke from the fire mixes with the clouds and gives them a yellow colour.

Finally, red, orange, or pink clouds usually appear at sunrise or sunset. These colours are caused by sunlight interacting with the atmosphere.

The colours of clouds can be used as signs of nature, as they can tell us about the conditions and weather changes within them.

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