Context:
Recently, NASA satellite captures ‘odd holes’ in clouds caused by aeroplanes
Cavum Clouds:
- Also known as hole-punch clouds or fallstreak holes
- Caused by – Aeroplane flight above clouds
- Aeroplanes pass through layers of altocumulus clouds, which contains supercooled water droplets
- As the aircraft moves through clouds, adiabatic expansion causes the water droplets to freeze into ice crystals
- These ice crystals eventually become too heavy and fall out of the cloud layer, creating a hole in the clouds
- When viewed from directly beneath typically a circular feature, but may appear oval shaped when viewed from a distance
Virga :
- Also known as wisps of Cirrus
- Ice crystals falling at the centre of the holes appear as delicate streaks of precipitation that never reach the ground
- It resembles rain or snowfall from clouds but evaporates before reaching the surface
Types of clouds:
| Clouds | Description |
| Cirrostratus | High, very thin, comprise a uniform layer, and are composed of ice crystals.Not easy to detect and is capable of forming halos when the cloud takes the form of thin cirrostratus nebulosus |
| Cirrocumulus | Small rounded puffs shapedUsually appear in long rows high in the sky and are white, but sometimes appear grey |
| Cirrus | High-altitude clouds with thin, feathery and wispy appearances Typically found at heights greater than 20,000 feet (6,000 meters)Composed of ice crystals that originate from the freezing of super cooled water droplets |
| Cumulonimbus | Dense towering and verticalTop part acquires an ‘Anvil Shape’Associated with thunderstorms and atmospheric instabilityFormed by water vapor carried by powerful upward air currents |
| Cumulus | Puffy, white clouds with a flat baseConvection-type and look like pieces of floating cottonTop part are round tower shapedOften associated with fair weather but can develop into larger storm clouds |
| Strato Cumulus | Low, lumpy clouds with a mix of elements from stratus and cumulus cloudsUsually arranged in large dark, rounded, or globular masses, usually in groups, lines, or waves |
| Stratus | Formed in uniform layers covering the sky, creating overcast conditionsUsually looks like a huge grey blanket that hangs low in the sky resembles fogIf these clouds are warm it means rain and if it is cold it snowsCan bring light rain or drizzle |
| Nimbostratus | Found as thick, dark clouds covering the skyOften associated with continuous rain or snow known as ‘Rain Clouds’Accompanied by light to moderately falling precipitation |
| Altostratus | Found in the form of continuous sheets or veils, grey or blue-gray at mid latitudesComposed of ice crystals and water dropletsSun can be visible as a round, dim disk in its thinner areaOften form ahead of storms with continuous rain or snow |
| Altocumulus | Found as greyish sheet-like cloudsCharacterized by globular masses or rolls in layers or patchesLarger and darker than those of cirrocumulus and smaller than those of stratocumulus |
Source: Hindustan Times
Previous Year Questions
Consider the following statements:
1. High clouds primarily reflect solar radiation and cool the surface of the Earth.
2. Low clouds have a high absorption of infrared radiation emanating from the Earth’s surface and thus cause warming effect.
Which of the statements given above is/are correct?
[UPSC Civil Services Exam – 2018 Prelims]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer: (d)
Explanation:
Statement 1 is not correct:
Low clouds primarily reflect solar radiation and cool the surface of the Earth.
Statement 2 is not correct:
High clouds have a high absorption of infrared radiation emanating from the Earth’s surface and thus cause warming effect.
