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UPSC Prelims 2022 · World Geography · Air, Winds and Climates
Consider the following statements: Which of the statements given above is/are correct?
- High clouds primarily reflect solar radiation and cool the surface of the Earth.
- Low clouds have a high absorption of infrared radiation emanating from the Earth's surface and thus cause a warming effect.
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Show the answer and explanation
Answer: (d) Neither 1 nor 2
Both reverse the roles of high and low clouds.
Statement by statement
1. ✗ WRONG HIGH clouds (cirrus) mainly trap outgoing heat and warm; it is low clouds that reflect sunlight and cool.
2. ✗ WRONG LOW clouds mainly reflect sunlight and cool the surface.
The idea
Clouds both reflect sunlight and absorb outgoing infrared radiation. The balance between these effects decides whether a cloud warms or cools the surface overall. Height changes the cloud-top temperature, while thickness changes its reflection of sunlight. The usual high-thin and low-thick comparison is a net effect, not an exclusive function.
Why the others are wrong
(c) Accepts both swapped statements.
The trap
Each statement describes the OTHER cloud type.
Also know
Albedo is the fraction of incoming sunlight reflected. Ice-crystal cirrus is a common high-cloud example; stratus and stratocumulus are common low clouds. Cloudy nights are often warmer because no incoming sunlight is available for the cooling effect. A tall cumulonimbus cannot be understood simply as a low or high thin layer.
🔒 High thin clouds warm; low thick clouds cool.
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