Question map
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 :
Explanation
The correct answer is option B (2 only).
**Statement 1 is incorrect** because the Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperature between two areas — a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia[1]. The statement wrongly mentions "tropical Eastern Pacific Ocean" instead of the eastern Indian Ocean, confusing IOD with ENSO characteristics.
**Statement 2 is correct** because an IOD phenomenon can influence an El Nino's impact on the monsoon[2]. This is further supported by evidence that a positive IOD index often negated the effect of ENSO, resulting in increased Monsoon rains in several ENSO years like 1983, 1994 and 1997[3]. The IOD can modify or counteract El Niño's typically adverse impact on Indian monsoons.
Therefore, only statement 2 is correct, making option B the right answer.
Sources- [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 29: El Nino, La Nina & El Nino Modoki > Indian Ocean Dipole Effect (Not Every El Nino Year Is The Same In India) > p. 415
- [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 29: El Nino, La Nina & El Nino Modoki > Impact of IOD On Cyclogenesis In Northern Indian Ocean > p. 417
- [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 29: El Nino, La Nina & El Nino Modoki > Indian Ocean Dipole Effect (Not Every El Nino Year Is The Same In India) > p. 416
PROVENANCE & STUDY PATTERN
Guest previewThis is a classic 'Definition Trap' question. UPSC loves to take a standard concept (IOD) and subtly swap a geographic location in the definition (Pacific instead of Indian Ocean). If you visualize the map while studying, this is a sitter; if you rote learn text, you get tricked.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- Explicitly defines IOD as the difference in sea surface temperature between a western pole (Arabian Sea/western Indian Ocean) and an eastern pole (eastern Indian Ocean south of Indonesia).
- Names the two poles (western and eastern Indian Ocean), directly answering which SST difference characterizes the IOD.
- Describes the sign of the SST difference (positive IOD: Arabian Sea warmer than Bay of Bengal; negative IOD: opposite), illustrating the west–east SST contrast.
- Links regional warming patterns to the dipole concept, reinforcing that the phenomenon is an SST difference across the Indian Ocean.
This statement analysis shows book citations, web sources and indirect clues. The first statement (S1) is open for preview.
Login with Google to unlock all statements.
This tab shows concrete study steps: what to underline in books, how to map current affairs, and how to prepare for similar questions.
Login with Google to unlock study guidance.
Discover the small, exam-centric ideas hidden in this question and where they appear in your books and notes.
Login with Google to unlock micro-concepts.
Access hidden traps, elimination shortcuts, and Mains connections that give you an edge on every question.
Login with Google to unlock The Vault.