UPSC Prelims 2002 Q12: Geography – Atmosphere & Climatology
For short - term climate prediction,
which one of the following events, detected in the last decade, is associated with occasional weak
monsoon rains in the Indian sub - continent?
- (a) La Niña
- (b) Movement of Jet Streams
- (c) El Niño and Southern Oscillations
- (d) Greenhouse effects on global level
Answer: (c) El Niño and Southern Oscillations
Explanation
Event linked with occasional weak monsoon rains
| Phenomenon | Link with the Indian monsoon |
|---|---|
| El Niño and Southern Oscillation (ENSO) | Warm Pacific water and low pressure shift the Walker cell; weak or failed monsoon in India |
| La Niña | Cooler Pacific; usually a good monsoon |
| Jet streams | Control monsoon onset and breaks, but are not a short-term predictor of weak years |
| Greenhouse effect | A long-term climate change factor, not a short-term event |
In El Niño years the pressure pattern of the Southern Oscillation weakens the monsoon flow, so rainfall in the Indian sub-continent falls. ENSO is therefore used for short-term prediction of weak monsoons. La Niña is usually associated with good rains.
Answer: (c) El Niño and Southern Oscillations.
Why each option is right or wrong
- (a) Incorrect. La Niña is usually linked with a strong monsoon.
- (b) Incorrect. Jet streams affect onset and breaks, not weak years as such.
- (c) CORRECT. El Niño with the Southern Oscillation brings weak monsoon rain.
- (d) Incorrect. The greenhouse effect is a long-term change, not a short-term event.
Key point
El Niño years: 1987, 2002, 2009 and 2014-15 saw deficient monsoons; the link is strong but not perfect.
Remember
El Niño usually weakens the Indian monsoon; La Niña strengthens it.
Common mistakes
- Choosing La Niña by confusing the two phases.
- Using greenhouse warming for a short-term question.
- Forgetting that not every El Niño gives a drought.
Exam tip
Short-term + weak monsoon = El Niño.
Sources
- India Meteorological Department — monsoon and ENSO
- NCERT Class XI — Fundamentals of Physical Geography