With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct ? 1. IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean. 2. An IOD phenomenon can influence an El Nino's impact on the monsoon. Select the correct answer using the code given below :
- (a) 1 only
- (b) 2 only ✓ UPSC's answer
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Why the answer is (b)
• The Indian Ocean Dipole is the difference in sea-surface temperature between the western tropical Indian Ocean (Arabian Sea) and the eastern tropical Indian Ocean (off Sumatra) — not the eastern Pacific, so statement 1 is wrong.
• Statement 2 is correct: a positive IOD (warmer west) favours monsoon rain and can offset an El Niño's drying effect, as in 1997; a negative IOD can worsen it.
• Hence 2 only, option (b).
Why the other options are wrong
- (a) 1 only
- Statement 1 is wrong: IOD is within the Indian Ocean, not the Pacific.
- (c) Both 1 and 2
- Statement 1 is wrong.
- (d) Neither 1 nor 2
- Statement 2 is correct: IOD modulates El Niño's monsoon impact.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2017, held on 18 June 2017. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.