Cloud Formation |6 Types of clouds | Cumulonimbus cloud

Clouds: provides shade, rain, snow, adds to the scenic beauty and acts as an envelope over the Earth. All these factors make us curious to discover more about clouds. So, lets begin.

Cloud Formation

The water vapours condense into tiny droplets to form clouds. The water molecules present in rising warm air cools and begins to clump together form tiny droplets. These droplets either remain suspended in air or combines with other droplets forming rain drops. In colder climates, this combined water droplets freeze to turn into ice crystals. 

The cloud formation depends on a number of environmental factors. Under special environmental and atmospheric conditions, clouds can produce tornadoes, hurricanes and severe storms.

Precipitation

When the combined water droplets become too heavy to remain suspended in air, they fall as precipitation. Generally, due to some atmospheric conditions, the water molecules swiftly combine to produce a large amount of rainfall. Snow, hail and freezing rain happen when the precipitated droplets freeze in the atmosphere before reaching the Earth’s surface.

Along with water molecules, at times, dust particles and certain chemicals present in the atmosphere also combine and reach the ground with rain. Under the right circumstances, all clouds can form rain. However, some form of clouds lie too distant for their precipitation to reach Earth.

 Two types of clouds that are generally responsible for precipitation are nimbostratus and cumulonimbus clouds. 

How do clouds move?

The spinning of the Earth affects the cloud movement. The spinning of the Earth affects the speed of wind at high altitudes and also the formation of tides. This wind movement is what makes the clouds move. 

Image Source: Wikipedia Commons

How fast do clouds Move?

Technically, the clouds are not the ones moving. Instead, it’s the air and wind that passes through clouds that moves. This movement of wind causes the clouds to move. In reality, if there were no wind moving, the water vapours won’t condense as the temperature would not be appropriate. However, every cloud cannot be moved. If the density of the cloud is appropriate, it withstand strong speeds. On the other hand, sometimes the clouds are so thin that the winds can break apart the clouds.

Colour of Clouds

Clouds are composed of water droplets, and therefore they are colourless in reality. The colours that we perceive clouds to have is due to the phenomenon of scattering. The colour of clouds differs depending upon its thickness. When sunlight falls on the clouds, the water droplets present, start scattering the light. 

White clouds

The thin or less dense clouds allow light to pass effortlessly through them and scatter rays of all colour equally (known as Mie scattering). These clouds appear to us as white.

Dark Clouds

Image Source: anonymous, Cosmópolis 0013 skyCC BY-SA 2.5

The thick or dense clouds scatter more light and allow less light to pass through them. These clouds appear as darker shades of grey.

Coloured clouds

Image Source: anonymous, WavecloudCC BY-SA 3.0

During dusk, sometimes the clouds appear to be pink, orange, red etc. This happens because at dust, shorter blue wavelengths are scattered before, and only the longer wavelengths predominantly reach the clouds. 

At times the presence of dust particles can cause both Rayleigh and Mie scattering. Due to this, clouds may appear coloured. 

Nimbus clouds

Nimbus refers to a Latin word that translates as rainstorm or cloud. Nimbus clouds are basically the greyish coloured clouds accountable for producing precipitation that falls in the form of hail, rain or snow. Nimbus clouds are dark in colour because they are filled with tiny droplets of water that fall down in the form of rain, sleet, hail or snow.

How are Nimbus clouds formed?

Nimbus clouds are formed as a result of condensation of water vapour into water droplets or ice crystals when the air cools. These water droplets then float in the atmosphere in a variety of shapes and sizes. The rate of condensation highly depends on the temperature and the movement of an air current. 

Types of Nimbus clouds:

Nimbus clouds can be further subcategorized into two types:

Cumulonimbus (cumulus clouds) 

Nimbostratus (stratus clouds).

Cumulonimbus clouds

Cumulonimbus clouds are known as “The King of Clouds” as they are menacing looking thunderclouds. These multi-level clouds extend across the entire height of the troposphere. The base of such clouds are dark and flattened, and the top is anvil-shaped. These clouds are responsible for producing heavy rain, hail, lightning and thunder.

Height: 1,100 – 6,500 ft

How does a cumulonimbus cloud form?

The process of convection forms cumulonimbus clouds. They often grow from small cumulus clouds gathered over a warm surface. These clouds can also form by forced convection along with cold fronts.

What is the weather linked with cumulonimbus clouds?

Cumulonimbus clouds are related with very extreme weather conditions such as hail storms, heavy torrential downpours, frequent lightning and even tornadoes at times. Once the showers start falling, individual cumulonimbus cells generally dissipate within an hour. A vast accumulation of cumulonimbus clouds can produce intense rainfall that can last for long. 

How do we categorize cumulonimbus clouds?

Cumulonimbus clouds can be further subcategorized into three types:

Cumulonimbus calvus – These type of clouds are puffy, like a cumulus cloud. These clouds do not have frozen water droplets or ice crystals. 

Cumulonimbus capillatus – These type of clouds are fibrous but relatively confined. In these clouds, water droplets just begin to freeze into ice crystals.

Cumulonimbus incus – These type of clouds are anvil-shaped and fibrous. These clouds continue to grow and reach high in the troposphere. 

Stratus Clouds

Stratus is Latin for flattened or spreads out. Stratus clouds are the nearly uniform light grey or low-level white layers of clouds. They can persist for long durations and often create a dull scene. These type of clouds are considered to be the lowest-lying and occasionally appear in the form of mist or fog near the surface.

 Height – 0-1200ft

How do stratus clouds form?

The most favourable conditions for Status clouds to form are a stable, calm environment with a gentle cool breeze and moist air covering the surface (both land and Ocean)

These clouds can vary in thickness. At times they are thick enough to envelop the surface allowing very little mount of light to pass through.

What is the weather linked with stratus clouds?

Stratus clouds generally contribute little to almost no rainfall. However, when it is thick enough, it may cause a little drizzle (rain or snow).

How do we categorize stratus clouds?

Stratus clouds can be further subcategorized into two types:

· Stratus nebulosus – This refers to the thick, dark layer of stratus clouds which is capable of producing drizzle.

· Stratus fractus – This refers to the stratus layer, which is thin, scattered and dissipated over an area.

Cirrocumulus clouds

Cirrocumulus clouds
Image Source: King of Hearts, Cirrocumulus clouds Thousand Oaks July 2010, CC BY-SA 3.0
Cirrocumulus cloud formation
Image Source: King of HeartsCirrocumulus clouds Thousand Oaks July 2010CC BY-SA 3.0

Cirrocumulus clouds are scarce and are composed of lots of small clouds or cloudlets. These cloudlets are grouped at high altitudes and appear as a honeycomb-like formation.

A very interesting thing about these cloudlets is that they are composed of ice crystals entirely.

Cirrocumulus clouds are sometimes referred to as mackerel sky because they look like the scaly fish skin. 

Height of base: 20,000 – 40,000 ft

How do cirrocumulus clouds form?

Cirrocumulus cloudlets are composed of both ‘supercooled’ water and ice. This shows that the water can remain a liquid at temperatures below 0 degree Celsius. 

Cirrocumulus cloudlets form when a cirrus layer meets turbulent vertical currents producing a puffy cumulus (heap-like) shape.

At times, Cirrocumulus clouds can form by the water vapour trails formed by aeroplanes as they fly across a dry troposphere. These streaks/trails can further spread out to become cirrostratus, cirrus and cirrocumulus.

What is the weather associated with cirrocumulus clouds?

Cirrocumulus clouds are formed at high altitudes, so its precipitation never reaches the surface.

 However, the appearance of Cirrocumulus clouds can often prelude stormy weather.

How do we categorize cirrocumulus clouds?

Cirrocumulus clouds can be further subcategorized into four types:

Cirrocumulus stratiformis – this refers to the patches or flat sheets of cirrocumulus, with regular separation producing a fish scale-like appearance.

Cirrocumulus lenticularis – this refers to the high-level icy lenses with a rounded shape. These are generally larger than altocumulus cloudlets. 

Cirrocumulus floccus – this refers to the fluffy rugged tufts of cirrocumulus that often occur in smaller patches.

Cirrocumulus castellanus – This refers to the tiny tower-like clouds in the sky.

Lenticular clouds

Lenticular clouds are strange, unnatural looking clouds that form downwind of hills or mountains at times. They appear similar to the traditional figure of flying saucers as seen various in science fiction. The real lenticular clouds are assumed to be one of the most popular justifications for UFO findings across the world.

Height: 6500 – 16500ft 

How are lenticular clouds formed?

In certain circumstances, air blows across mountain ranges setting up a train of standing waves downstream. These waves appear like ripples forming in a river. In the presence of sufficient moisture, these waves contribute to condensing water vapour into uniquely shaped lenticular clouds.

What is the weather associated with lenticular clouds?

Lenticular clouds act as a sign of mountain waves in the sky. However, there is a possibility of such waves to exist beyond the clouds and may be present even when there are no clouds.

Lenticular clouds may cause strong winds in one place and almost stationary air some hundred meters away. Due to this, pilots avoid flying near lenticular clouds.

How do we categorize lenticular clouds?

Lenticular clouds can be further subcategorized into three types depending on the altitude:

· Standing lenticular (ACSL),

· Stratocumulus standing lenticular (SCSL), 

· Cirrocumulus standing lenticular (CCSL)

Nacreous Clouds

Nacreous Cloud formation
Image source: Wikimedia Commons

Nacreous clouds, also known as mother-of-pearl clouds, are ice polar stratospheric clouds. These clouds are known for their brilliant colours suring the time the sun lies beneath the horizon. 

How are Nacreous clouds formed?

Nacreous cloud formation takes place mainly during the winters at high latitudes when the temperature in the stratosphere falls below the frost point. These clouds are composed of approximately equal-sized spherical water droplets. 

To know more about clouds and fog visit https://lambdageeks.com/clouds-and-fog/

About Sanchari Chakraborty

I am an eager learner, currently invested in the field of Applied Optics and Photonics. I am also an active member of SPIE (International society for optics and photonics) and OSI(Optical Society of India). My articles are aimed towards bringing quality science research topics to light in a simple yet informative way. Science has been evolving since time immemorial. So, I try my bit to tap into the evolution and present it to the readers.

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