Previous Year Question
With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct?
OMT is measured up to a depth of 26°C isotherm which is 129 meters in the South-western Indian Ocean during January to March.
OMT collected during January to 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 codes given below:
Correct Answer: B
Detailed Solution
Ocean Mean Temperature or OMT is the average temperature of the oceanic layer extending from the surface to the depth of the 26°C isotherm (D₂₆). Instead of representing only the surface temperature, it indicates the thermal energy stored in the upper ocean.
Statement 1 is incorrect: OMT is calculated up to the depth of the 26°C isotherm, but its January-March climatological mean depth in the southwestern Indian Ocean is approximately 59 metres, not 129 metres. This depth also varies according to location and time.
Statement 2 is correct: The January-March OMT of the southwestern Indian Ocean helps in making a qualitative assessment of whether Indian summer monsoon rainfall will be below or above its long-term mean.
A scientific study found that OMT had an approximately 80% success rate in indicating above- or below-average monsoon rainfall, compared with approximately 60% for Sea Surface Temperature or SST. This is because SST represents only a thin surface layer and is quickly affected by winds, evaporation and clouds, whereas OMT better represents the heat stored in the upper ocean.