Cloud Formation, Rain Types & Island

Cloud Formation, Rain Types & Island

Clouds 

Clouds are defined as aggregates of innumerable tiny water droplets, ice particles, or a mixture of both in the air, generally much above the ground surface. They play a vital role in the heat budget of the Earth.

Based on the average height, clouds are classified into:

1. High Clouds (Height: 42,500 ft. to 16,500 ft or 13 to 5 km, according to Encyclopaedia Britannica)

Cirrus Clouds

• The high-altitude detached clouds with having fibrous (chain-like) or silky appearance are called cirrus clouds.

• They are composed of tiny crystals. Therefore, they do not cause rainfall.

• These clouds are indicators of cyclones.

Cirrocumulus

• These are white coloured clouds having patches of small white flakes or globules arranged in distinct groups or wave-like form.

• They generally appear as ripples similar to sand particles in the desert.

Cirrostratus Clouds

• These clouds are generally white in colour and spread in the sky like milky thin sheets.

• Cirrostratus is a thin veil of cirrus clouds.

• These are transparent clouds and create halos around the Sun and the Moon.

• They are seen just after the cirrus cloud at the onset of a cyclone, indicating the arrival of a cyclone.

2. Middle Clouds (Height: 23,000 ft. to 6,500 ft. or 7 km to 2 km)

Altostratus Clouds

• These are thin sheets of grey or blue clouds having a fibrous or uniform appearance.

• When they become thick, the Sun and Moon are obscured and appear as bright spots behind the clouds.

• They yield widespread and continuous precipitation.

Altocumulus Clouds

• These clouds are characterized by white and grey wavy layers or globular forms.

• They form regular patterns of lines, groups, or waves.

• High globular groups of altocumulus are sometimes called Sheep clouds or Wool pack clouds.

3.  Low Clouds (Height: 6,500 ft to 0 feet or 2 km to 0 km)

Stratus Clouds

• These are dense, low-lying fog-like clouds of dark grey colour close to the ground surface.

• They are composed of several uniform layers.

• These clouds are formed in the subtropical region during winter due to the convergence of opposite air masses.

• When these clouds are associated with rain or snow, they are called nimbostratus clouds.

Cumulostratus Clouds

• These are light grey or whitish clouds generally composed of globular masses or rolls arranged in lines, waves, or groups.

• They cover the entire sky in winter and are associated with fair weather.

Cumulus Clouds

• These are dense, widespread, and dome-shaped clouds with flat bases.

• They are associated with fair weather.

Cumulonimbus Clouds

• These are thunderstorm clouds that are very dark, dense and show great vertical development.

• They are associated with heavy rainfall, hailstorms, thunder, etc. Rainfall in tropical and temperate cyclones is generally caused by these clouds.

Nimbostratus Clouds

• These are low, dark-coloured clouds very close to the ground surface.

• They block sunlight due to their thickness, increase humidity, and cause precipitation. Rainfall in subtropical cyclones is generally caused by these clouds.

Rainfall

Rainfall occurs only when cloud droplets become so large due to coalescence that the air becomes unable to hold them. Based on the mode of origin, rainfall is classified into three types:

1. Conventional Rainfall

• When the land surface is heated, the air in contact rises, creating convectional currents.

• As this warm and moist air reaches a certain height, it becomes saturated and forms dark Cumulonimbus clouds that cause heavy rainfall.

• This occurs in the equatorial belt, especially in the zone of the Doldrums.

2. Orographic or Relief Rainfall

• This occurs when hills or mountains obstruct warm and moist air, forcing it to ascend along slopes.

• As it cools, condensation starts causing rainfall, known as orographic rainfall.

3. Cyclonic or Frontal Rainfall

• This is caused by the convergence of warm and cold air masses with different physical properties.

• The warm air is lifted upward along the front where it cools and condenses, resulting in heavy rainfall.

Islands

Land masses surrounded by water from all sides are called Islands. A group of islands is called an archipelago. Based on their origin, islands are classified into:

1. Tectonic Islands

• Formed due to subsidence or upliftment of land, forming one of the rift valleys, or segmentation of continental parts caused by tectonic activities.

• Example: West Indies.

2. Volcanic Islands

• Formed when a volcanic eruption deposits material in a water body until it emerges above the surface.

• Example: Hawaiian Islands.

3. Erosion Islands

• Soft rocks erode easily, leaving hard rock portions surrounded by water.

• Example: Greenland.

4. Depositional Islands

• Formed by the deposition of sediments by rivers, glaciers, or sea waves.

5. Coral Islands

• Formed by the accumulation of coral polyps on submarine platforms in tropical oceans.

• Example: Lakshadweep, Maldives.

Final Thoughts

The study of clouds, rainfall, and islands gives us valuable insight into how nature shapes our world. Clouds not only influence weather patterns but also play a vital role in maintaining Earth’s heat balance. By understanding the types of clouds and their characteristics, we can predict weather conditions more accurately.

Rainfall, in its various forms – convectional, orographic, and cyclonic – shows how geography and atmospheric conditions work together to create precipitation. Similarly, the formation of islands – whether volcanic, coral, or tectonic – demonstrates the immense power of natural forces over time.

Learning these concepts helps us appreciate the dynamic relationship between land, air, and water on our planet. Mastering these fundamentals is essential for students and enthusiasts who want to explore climate science, weather forecasting, or Earth’s geography.