Prelims 2020 · Q93
HardWith reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct?
- 1.OMT is measured up to a depth of 26°C isotherm which is 129 meters in the south-western Indian Ocean during January – March.
- 2.OMT collected during January – March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.
Select the correct answer using the code given below:
Answer & explanation
Answer: (b) 2 only
Statement 2 is right and statement 1 is wrong. OMT (the average temperature of the ocean from the surface down to the 26°C isotherm) in the south-western Indian Ocean during January–March helps predict whether the coming monsoon rainfall will be above or below average, but the 26°C isotherm there lies at about 59 m, not 129 m.
- ✗ 1. OMT is the mean temperature of the layer from the surface down to the 26°C isotherm, which is the first half of the statement. But the January–March climatic mean depth of that isotherm in the south-western Indian Ocean is about 59 m, not 129 m.
- ✓ 2. The January–March south-western Indian Ocean OMT is a better qualitative predictor of Indian summer monsoon rainfall than sea surface temperature; it correctly signals above-average or below-average rain about 80% of the time, against 60% for SST.
Remember · OMT = mean temperature from the surface to the 26°C isotherm; south-western Indian Ocean OMT in January–March forecasts monsoon rain (isotherm depth about 59 m there).
Sources
- Venugopal et al., 'Statistical Evidence for the Role of Southwestern Indian Ocean Heat Content in the Indian Summer Monsoon Rainfall', Scientific Reports 8:12092 (2018), open-access copy on PubMed Central (NIH) ↗ “Here, we show that the southwestern Indian OMT down to the depth of the 26 °C isotherm during January–March is a better qualitative predictor of the ISMR than SST. … The January–March climatic mean D 26 is 59 m and the corresponding OHC is 50 kJ cm −2 in this region.”
Question and answer: UPSC's official GS Paper I (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·