Question

UPSC Prelims 2019 Question:

Why are dewdrops not formed on a cloudy night?

1. Clouds absorb the radiation released from the Earth’s surface.
2. Clouds reflect back the Earth’s radiation.
3. The Earth’s surface would have low temperatures on cloudy nights.
4. Clouds deflect the blowing wind to ground level.

Answer (Detailed Solution Below)

Option 2: Clouds reflect back the Earth’s radiation.

Detailed Solution

Explanation: Dew is a moisture condensed from the atmosphere, especially at night. It is deposited in the form of small drops upon any cool surface.

The favorable weather elements for dew include clear skies, light wind, decent soil moisture and long cold night-time.
Clear sky allows the escape of the radiation from the Earth’s surface. Thus, it keeps the night cold for a long time. On the contrary, clouds reflect back radiation to the Earth surface which increases the temperature. This enhanced temperature is not favorable for dew formation. Thus, cloudy nights and warm surface temperature obstruct the dew formation.

Therefore, option (2) is the correct answer.

Subject: Geography | Climate Weather and Atmosphere

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