Prediction of Indian Summer Monsoon
08, Sep 2018
Prelims level : Mains level : Paper – I Geography
Scientists from Pune’s Indian Institute of Tropical Meteorology (IITM) find that ocean mean temperature (OMT) can better predict Indian summer monsoon than the sea surface temperature.
- Compared with Sea surface temperature (SST) which has 60% success rate of predicting the Indian summer monsoon, ocean mean temperature (OMT) has 80% success rate.
- In addition to better predictive success, the information on whether the amount of monsoon rainfall will be more or less than the long-term mean will also be done.
- The variations in the upper ocean thermal energy conditions are mainly responsible for summer monsoon activity. As sea surface temperature gives information only about the thin upper layer of the ocean and does not reflect the thermal energy available in the upper ocean.
- The heat content of the upper ocean creates more impact on monsoon than sea surface temperature, which is restricted to the skin of the ocean.
- The SST is restricted to a few millimetres of the top ocean layer and is largely influenced by strong winds, evaporation, or thick clouds. 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 OMT performs better than SST is because OMT better represents the upper ocean thermal energy conditions. And the variations in the upper ocean thermal energy conditions are mainly responsible for the summer monsoon.
- “When there is rapid heating or cooling, the temperature of the top ocean layer will be significantly different from the upper ocean thermal energy, resulting in misleading monsoon prediction.
- SST also exhibits large temperature fluctuations compared with OMT of the upper layer, leading to more noise that causes lower correlations with summer monsoon rainfall. The ocean mean temperature variations are more stable and consistent and have lower spatial and temporal spread. So OMT has better summer monsoon predictability than SST