UPSC Prelims 2002 Q9: Geography – Atmosphere & Climatology
Consider the following climatic and geographical phenomena:
1. Condensation
2. High temperature and humidity
3. Orography
4. Vertical wind
Thunder - cloud development is due
to which of these phenomena?
- (a) 1 and 2
- (b) 2, 3 and 4
- (c) 1, 3 and 4
- (d) 1, 2, 3 and 4
Answer: (d) 1, 2, 3 and 4
Explanation
Phenomena responsible for thunder-cloud development
| Phenomenon | Role in a thunderstorm |
|---|---|
| High temperature and humidity | Warm moist air gives the energy and water vapour |
| Orography | Hills force air to rise and trigger convection |
| Vertical wind | Strong updraughts carry the air to great heights |
| Condensation | Releases latent heat that builds the cumulonimbus |
A cumulonimbus (thunder-cloud) needs moist unstable air, a trigger to lift it, strong vertical motion and condensation that releases latent heat. All four listed phenomena contribute, so the correct choice is 1, 2, 3 and 4.
Answer: (d) 1, 2, 3 and 4.
Why each option is right or wrong
- (a) Incorrect. Condensation and humidity alone leave out the lifting agents.
- (b) Incorrect. It leaves out condensation, which releases the latent heat.
- (c) Incorrect. It leaves out the high temperature and humidity that supply moisture.
- (d) CORRECT. All four phenomena contribute.
Key point
Thunderstorm ingredients: moisture, instability, lifting mechanism (orography, fronts, convection).
Remember
Thunder-cloud = heat + humidity + lift + vertical wind + condensation.
Common mistakes
- Choosing 1, 3 and 4 and treating humidity as a side factor.
- Forgetting that latent heat of condensation fuels the storm.
- Thinking orography matters only for orographic rain.
Exam tip
When every item is a genuine ingredient, 'all of the above' is usually the key.
Sources
- NCERT Class XI — Fundamentals of Physical Geography (Atmospheric circulation and weather systems)
- Savindra Singh — Climatology (Prayag Pustak Bhawan)