4 Oct 2016 | GS1 | The IMD recently got its forecast for this year wrong. India will now get 3% less rain than normal. What are the phenomena that result in variations in Indian monsoon.

GS1 (Indian Geography)

The IMD recently got its forecast for this year wrong. India will now get 3% less rain than normal. What are the phenomena that result in variations in Indian monsoon.

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The Indian monsoon can be understood as the seasonal reversal of winds in south Asian region across Tibetan plateau to Masacrnes Islands, that result in the rainfall winds from south west causing rainfall over India in the post summer months.

Being a seasonal reversal, it has various season to season variations that can be caused by:
1. El-Nino: It refers to the above average heating of ocean waters in the west Pacific. Has negative correlation with intensity of S-W monsoon.
2. La-Nina: It is the resetting of normal conditions, post El-Nino. Has positive correlation with strong S-W monsoon.
3. Madden-Jullian Oscillations: Mobing air mass over Pacific and Indian Ocean surfaces – results in positive effect on Indian Monsoon.
4. International Date Line El-Nino: negates the effect of standard el-Nino.
5. Indian Ocean Dipole: Has negative correlation with strong Indian monsoon. It is essentially the see saw condition of water temperature over the Indian Ocean.
6. Tropical Easterly Jet stream: It’s disappearance is closely related to the onset of monsoon.
7. Less than optimal heating of Tobetan Hogh – causes lesser intensity of rainfall and the anti cyclone is weaker.
8. Southern Indian Ocean atmospheric conditions , when disturbed due to the rogue wave and fierce westerlies – decrease the high pressure there.

Apart from these urban ecosystem, especially cutting of palm forests in Indonesia, disturb in the Leeuwin current cycle due to coral reef degradation, and excess of particular matter in the atmosphere that results in rainless clouds are also responsible for variations in the intensity and temporal and space variations.

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