Clouds

Different Types Of Clouds

Clouds change continuously. They appear in a huge variety and in infinite forms. The WMO – World Meteorological Organization has classified clouds into ten main groups termed as genera. Depending upon the atmospheric part in which clouds are generally found, the three levels into which clouds are classified are:

CL – Cloud Low

In the Low Cloud level the different cloud types are Stratocumulus, Stratus, Cumulus and Cumulonimbus. Their base lies usually below 6500 feet over land.

CM – Cloud Medium

In the Medium cloud level the different cloud types are Altocumulus, Altostratus and Nimbostratus. Their base lies usually between 6,500 and 20,000 feet above land.

CH – Cloud High

In the High cloud level the different cloud types are Cirrus, Cirrocumulus and Cirrostratus. Their base lies usually 20,000 feet or above land.

Clouds take different kinds of shapes. They have different kinds of internal structure which has let to subdividing them in various cloud genera species.

A combination of various suffixes or prefixes is provided to give names to different types of clouds.

Types Of Clouds

• Nimbo - Rain Bearing Clouds

Nimbostratus clouds are blue and grey in colour, and are clouds without features. They are so thick that they block out the sun’s rays. Heavy snow and rain accompany these mid level clouds. When lighting, thunder or hail accompanies it then it becomes a nimbostratus cloud.

• Strato / Stratus – Smooth, Layered Or Flat Clouds

Strato clouds have the appearance of a rounded, dark and large mass in waves, lines or groups, usually. They are shallow layers of clouds due to stable and dry air which prevent their continual vertical development.

Stratus is a patch or low level clump of cloud. It varies from dark grey to bright white colour. The base is well defined and some of the parts are darker as compared to the rest. The stratus clouds are patches of grey and low level clouds having fuzzy edges. They appear in the form of fog or mist at ground level and snow grains, snow or drizzle may accompany these clouds.

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• Cumulo / Cumulus - Puffy Or Heaped Up, Cauliflower-Like Clouds

Cumulonimbus are dense, heavy, low level clouds or thunderclouds extending high into the sky in plumes, tower or peaks in mountain shape. Hail storms, heavy torrential downpour, tornados and lighting accompany the cumulonimbus clouds.

Cumulus clouds come in the shape of a detached cauliflower and are seen mainly in fair weather. Showers are produced if they get bigger. When lit by the sun, the top of the cloud is brilliant white while the base remains relatively dark.

• Cirro / Cirrus – Wispy Or High Up Clouds

Cirrocumulus clouds are cloudlets or white clouds composed of ice crystals and form at high levels in groups. They don’t have any shading.

Cirrus is hair-like, delicate, detached, short, wispy clouds that look like tufts of hair and have a silky sheen. In the sky they are whiter as compared to any other cloud. They take on the colours of the sunset, at times.

• Alto – Medium Level Clouds

Altocumulus are grey or white cloudlets or small patches or mild level layers of clouds which appear in the form of rounded clumped shapes. Their sides are shaded and remain away from the sun and are generally seen in settled weather.

Altrostratus are blue or grey coloured, thin, mid level clouds composed of a mixture of crystals of ice and droplets of water. They are so thin that even a weak sun can be seen through the cloud. These clouds are featureless and extend to thousands of square miles.

What Is A Cloud

Clouds are crystals of ice or tiny drops of water that settle on particles of dust in the atmosphere. Size of the water drops is extremely small – about a diameter of about a 100th of a millimetre. Around 100 million water droplets are contained in every cubic meter of air. Depending upon the clouds height and the atmospheric temperature, water droplets or ice is contained within the clouds. At times the droplets are so tiny that they continue to remain in the form of liquid in low temperatures ranging up to -30 °C. When the temperatures go below -30 °C, the clouds are composed of crystals of ice. These clouds are extremely high clouds.

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Cloud Formation

When invisible water vapour present in the air, undergoes condensation and become crystals of ice or droplets of water, clouds are formed. All around you, water is present in the form of very tiny particles of gas, also termed as water vapour. Dust or salt also are the other forms of tiny particles, called aerosols that float around in the air. The aerosols and the water vapour keep bumping into each other, constantly. When cooling of air takes place, some amount of the water vapour collides on to the aerosols and sticks on them, in a process called condensation. Due to this condensation, bigger droplets of water start forming around the particles of aerosol which leads to the formation of clouds.

When there is saturation in the air and the air cannot hold any more of the water vapour, then clouds are formed.

Different Ways Clouds Are Formed

Clouds are formed in two different ways

Clouds are formed when there is an increase of amount of water in the air. There comes a point when the air is not able to hold any more water, leading to cloud formation.

Clouds are formed when condensation occurs. The air cools to its dew point and is not able to hold any more water.

More water vapour can be held by the air, if it is warmer. It is through condensation that production of clouds takes place. When air rises, it starts cooling, it reduces air temperature, due to which it is not able to hold water and leads to the occurrence of condensation. Condensation level is the height at which dew point is attained and clouds are formed.

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Why Do Clouds Form?

There are five factors responsible for rising of air, cooling of air and formation of clouds.

• Turbulence

At times due to height levels, the speed of wind changes suddenly. In the air turbulent eddies are thus created.

• Orographic forcing or topography

Features or shape of an area, or the topography leads to formation of clouds. When there are mountains or hills, air is forced to rise and as it rises, it cools, leading to the formation of layered clouds.

• Heating of surface

Due to the sun’s heat, the ground gets heated which in turn, heats the air which comes in contact with it leading to rising of air. Cumulus clouds are produced with these rising columns of air, termed as thermals.

• Convergence

At times streams of air coming from various directors, rise, while converging or flowing together. This leads to showery conditions or formation of cumulus clouds.

• Frontal

At times a mass or warmed up air, rises along fronts over large areas or over a cloud mass, leading to the forming of clouds. The boundary between drier, cooler, moist and warm air is termed as a ‘front’.

The atmosphere is variable by nature and the range at which the clouds form, results in clouds of different textures, sizes, shapes and varieties.

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