UPSC Prelims 2011 Q52: Geography – Atmosphere & Climatology
La Nina is suspected to have caused recent floods in Australia. How is La Nina different from
El Nino ?
1. La Nina is characterised by unusually cold ocean temperature in equatorial Indian Ocean
whereas El Nino is characterised by unusually warm ocean temperature in the equatorial Pacific
Ocean.
2. El Nino has adverse effect on south - west monsoon of India, but La Nina has no effect on
monsoon climate.
Which of the statements given above is/are correct ?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (d) Neither 1 nor 2
Explanation
La Nina vs El Nino: checking both statements
La Nina and El Nino are opposite phases of the same Pacific Ocean climate pattern, not an Indian Ocean phenomenon.
| Statement | Verdict | Reason |
|---|---|---|
| 1. La Nina = cold in equatorial Indian Ocean; El Nino = warm in equatorial Pacific | Incorrect | Both La Nina and El Nino are Pacific Ocean phenomena (equatorial Pacific), not the Indian Ocean; statement wrongly places La Nina in the Indian Ocean |
| 2. El Nino hurts India's monsoon; La Nina has no effect | Incorrect | La Nina is not neutral; it typically favours/strengthens the Indian south-west monsoon, giving above-normal rainfall, rather than having 'no effect' |
El Nino/La Nina and India's monsoon:
| Phase | Ocean region | Typical monsoon effect |
|---|---|---|
| El Nino | Warm equatorial Pacific | Weakens monsoon, often drought-linked |
| La Nina | Cold equatorial Pacific | Generally strengthens monsoon (above-normal rain) |
Answer: (d) Neither 1 nor 2.
Why each option is right or wrong
- (a) Incorrect. Statement 1 wrongly locates La Nina's cold anomaly in the Indian Ocean; both phenomena are Pacific Ocean-based.
- (b) Incorrect. Statement 2 wrongly claims La Nina has no monsoon effect; it typically strengthens the monsoon, not a neutral 'no effect'.
- (c) Incorrect. Neither statement is factually accurate, so 'both' cannot be correct.
- (d) CORRECT. Statement 1 misplaces the ocean (Pacific, not Indian), and statement 2 wrongly denies La Nina's positive monsoon effect.
Key point
Both La Nina and El Nino are PACIFIC OCEAN phenomena (not Indian Ocean); La Nina generally STRENGTHENS India's monsoon rather than having 'no effect'.
Remember
El Nino and La Nina are both equatorial PACIFIC Ocean phenomena; La Nina generally STRENGTHENS, not ignores, India's monsoon.
Common mistakes
- Placing La Nina's temperature anomaly in the Indian Ocean instead of the Pacific.
- Assuming La Nina is monsoon-neutral, when it usually boosts rainfall.
- Not recognising El Nino and La Nina as opposite phases of the same Pacific phenomenon (ENSO).
Exam tip
El Nino/La Nina = Pacific Ocean phenomena, always. La Nina tends to help, not ignore, India's monsoon.
Sources
- India Meteorological Department — El Nino/La Nina and Indian monsoon advisory
- National Oceanic and Atmospheric Administration (NOAA) — ENSO explainer