Climatology: Atmosphere, Weather and Climate› Insolation, Heat Budget and Temperature Distribution
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?
Answer d.
The answer is (d) Neither 1 nor 2. Both statements swap the roles of the two cloud types: it is low, thick clouds that reflect sunlight and cool the surface, while high, thin clouds let sunlight through and trap outgoing infrared, warming the surface. Clouds affect the heat budget in two opposite ways depending on their height and thickness. Low, thick clouds (stratus, nimbostratus) have a high albedo: they reflect a large share of incoming short-wave solar radiation back to space, so their net effect is cooling. High, thin clouds (cirrus, made of ice crystals) are largely transparent to incoming sunlight but absorb the long-wave infrared radiation emitted by the Earth's surface and re-radiate part of it downward, so their net effect is warming. Statement 1 gives high clouds the low-cloud role, and statement 2 gives low clouds the high-cloud role, so both are wrong. This follows from the heat-budget discussion in NCERT Class 11 Fundamentals of Physical Geography, Ch. 9 (Solar Radiation, Heat Balance and Temperature).
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