Ocean Mean Temperature (OMT) vs Sea surface temperature (SST)
Sea surface temperature (SST) is routinely used for predicting whether the total amount of rainfall that India receives during the monsoon season will be less or more than the long-term mean of 887.5 mm.
Ocean Mean Temperature (OMT) – which is analysed by measuring the ocean thermal energy during the January-March period – can better predict Indian summer monsoon than the SST.
The SST is restricted to a few millimetres of the top ocean layer and is largely influenced by strong winds, evaporation, or thick clouds. Also, it does not reflect the thermal energy available in the upper ocean.
In contrast, OMT, which is measured up to a depth of 26-degree C isotherm, is more stable and consistent, and the spatial spread is also less. The 26-degree C isotherm is seen at depths varying from 50–100 metres.