Climatology: Clouds and Types

Definition: A cloud is an accumulation or grouping of tiny water droplets and ice crystals that are suspended in the earth’s atmosphere.
Formation: Clouds are formed when the air becomes saturated or filled, with water vapour. The warm air holds more water vapour than cold air.
Significance of Clouds
- They are needed for production of precipitation.
- During the nights, clouds reflect heat to the earth and keep the temperature warm.
- During the day, clouds help in keeping the temperature cooler by shielding the sunlight.
- Researching and studying clouds helps in understanding weather and climate.

Classification Based on Shape
- Cirrus Clouds
  - Cirrus clouds are formed at high altitudes of 8,000 – 12,000m.
  - They are detached thin clouds.
  - They have a feathery appearance.
  - They are always white.
- Cumulus Clouds
  - Cumulus clouds are generally formed at a height of 4,000 m – 7,000 m.
  - They look like cotton wool.
  - They exist in patches and can be seen dispersed here and there.
  - They have a flat base.
- Stratus Clouds
  - Stratus clouds are horizontal.
  - Stratus clouds are stratified or layered clouds covering big portions of the sky.
  - These clouds are usually formed due to the mixing of air masses with various temperatures or due to loss of heat.
  - The presence of stratus clouds means chilly.
- Nimbus Clouds
  - Nimbus clouds are usually formed at lower altitudes.
  - The colour of Nimbus clouds is usually black or dark grey.
  - These types of clouds usually cause heavy rainfall and thunderstorms.
Classification of Clouds Based on Altitude
- High Clouds
  - They can reach above 6000 metres or 20,000 feet.
  - They are also known as Cirrus Clouds.
  - They are usually thin and are made up of ice.
  - They often indicate fair weather and hence do not produce rain.

Type of cirrus clouds	Features
Cirrus	They are thin and often wispy cirrus clouds. Typically found at heights greater than 6,000 meters, they are composed of ice crystals that originate from the freezing of supercooled water droplets
Cirrostratus	They are high, very thin, comprises a uniform layer, and are composed of ice-crystals. It is difficult to detect and is capable of forming halos when the cloud takes the form of thin cirrostratus nebulosus.
Cirrocumulus	They are small rounded puffs shaped clouds, that usually appear in long rows high in the sky and are usually white, but sometimes appear grey.

- Middle Clouds
  - They are found from 2000 to 6000 metres.
  - They are also known as “Alto” clouds.
  - They frequently indicate an approaching storm.
  - They may sometimes produce Virga, which is a rain or snow that does not reach the ground.

Type of Alto Clouds	Features
Altostratus	These clouds are in the form of continuous sheet or veil, grey or blue-gray in colour. They are composed of ice crystals and water droplets. In its thinner areas, the sun can still be visible as a round, dim disk. These clouds may often form ahead of storms with continuous rain or snow.
Altocumulus	They are greyish sheet cloud, characterised by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus.

- Low Clouds
  - They are found from the surface to 2,000 meters.
  - They are also known as Stratus Clouds.
  - They may appear dense, dark, and rainy (or snowy) and can also be cottony white clumps interspersed with blue sky.

Type of Stratus Clouds	Features
Strato Cumulus	Arranged in a large dark, rounded or globular masses, usually in groups, lines, or waves.
Stratus	Looks like a huge grey blanket that hangs low in the sky that resembles fog, comprises uniform layer and appear dull, if these clouds are warm it means rain and if it is cold it snows.
Nimbostratus	They are known as ‘Rain Clouds’ and they are dark, thick and accompanied by light to moderately falling precipitation.