UPSC Prelims 2011 · Question 22 of 100
UPSC Prelims 2011 question on La Nina
- ExamUPSC CSE
- Year2011
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicClimatology
- DifficultyMedium
- TypeStatement
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?
Show answer
Answer: D. Neither 1 nor 2
Verdict
Correct Answer: Neither 1 nor 2
Both statements are incorrect because they wrongly describe the location and monsoon impact of El Niño and La Niña.
Statement by statement
1. Statement 1 — Incorrect
El Niño and La Niña do not occur in the Indian Ocean. They occur in the central and eastern equatorial Pacific Ocean.
They are opposite phases of the El Niño-Southern Oscillation (ENSO).
El Niño: abnormal warming of surface waters in the central/eastern equatorial Pacific.
La Niña: abnormal cooling of surface waters in the central/eastern equatorial Pacific.
2. Statement 2 — Incorrect
La Niña does affect the Indian monsoon. The statement saying it has “no effect” is wrong.
El Niño generally weakens the South-West Monsoon and may cause deficient rainfall or drought-like conditions in India.
La Niña generally strengthens the South-West Monsoon and may cause above-normal rainfall, floods, and intense rainfall events.
Extra UPSC info
ENSO has three phases: El Niño, La Niña, and Neutral phase.
El Niño is linked with weak trade winds, reduced upwelling near South America, and warmer Pacific waters.
La Niña is linked with stronger trade winds, stronger upwelling, and cooler Pacific waters.
ENSO influences rainfall, droughts, floods, agriculture, food prices, and disaster management in India.
A separate phenomenon called the Indian Ocean Dipole (IOD) occurs in the Indian Ocean.
A positive IOD can sometimes reduce the negative impact of El Niño on the Indian monsoon.
How to crack it
El Niño and La Niña occur in the Pacific Ocean, not the Indian Ocean. Both affect the Indian monsoon, with El Niño generally weakening it and La Niña generally strengthening it. Therefore, the correct answer is Neither 1 nor 2.