The impact of global warming on the monsoons are visible in the onset, withdrawal, its seasonal total rainfall, and its extremes. Global warming also affects the cyclones over the Indian Ocean and the cyclone’s position affect monsoon’s onset.

Impact of global warming on Indian Monsoon -

Ø  Alarming increase in floods and droughts provides direct evidence of how global warming has been impacting the Indian monsoon.

Ø  While summer monsoon rainfall each year is unique, there was a large regional and temporal variability in rainfall last year.

Ø  There is evidence that global warming increase the fluctuations in the monsoon, resulting in both long dry periods and short spells of heavy rains.

Ø  The monsoon is also affected by the three tropical oceans— Indian, Atlantic, and Pacific; the ‘atmospheric bridge’ from the Arctic; and the oceanic tunnel as well as the atmospheric bridge from the Southern Ocean (a.k.a. the Antarctic Ocean). A ‘bridge’ refers to two faraway regions interacting in the atmosphere while a ‘tunnel’ refers to two remote oceanic regions connecting within the ocean.

Cyclone and Impact of Global Warming on Cyclones -

Ø  Cyclones are rapid inward air circulation around a low-pressure area.

Ø  The air circulates in an anticlockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere.

Ø  Cyclone are forming in the pre-monsoon season, closer to the monsoon onset, arguably due to the influence of a warmer Arctic Ocean on the winds over the Arabian Sea.

How does a Cyclone’s position affect Monsoon’s onset?

Ø  Some cyclones in the North Indian Ocean have had both positive and negative impacts on the onset of the monsoon.

Ø  Since the circulation of winds around the cyclones is in the anticlockwise direction, the location of the cyclone is critical as far as the cyclone’s impact on the transition of the monsoon trough (a low-pressure region) is concerned.

Ø  If a cyclone lies further north in the Bay of Bengal, the back-winds blowing from the southwest to the northeast can pull the monsoon trough forward, and assist in the monsoon’s onset.

Ø  For example, Cyclone Mocha which developed in the first half of May and intensified briefly into ‘a super cyclonic storm.’ Mocha’s north-west to east trajectory was due to unusual

Ø  anticyclones which rotate clockwise. Mocha dissipated on May 15 and the back-winds helped the monsoon set in on time over the Andaman and Nicobar Islands.

Ø  One severe consequence of the anticyclones since March is that both the Arabian Sea and the Bay of Bengal have warmed by more than 1-degree Celsius in the pre-monsoon season.

Impact of southwesterly winds on Indian Monsoon -

Ø  Southwesterly winds over the Arabian Sea are welcome news because they bring large quantities of moisture onto the Indian subcontinent.

Ø  On the other hand, southwesterly winds over the Bay of Bengal are bad news for the monsoon. The monsoon winds over the southern Bay of Bengal sweep in from the southwest and west, but they turn around and head northwest towards India from the southeast.

Ø  The strong southwesterly winds over the Bay of Bengal can be imagined to be a very large highway with heavy traffic heading —

Ø  From the southwest, over southern peninsular India and Sri Lanka,

Ø  Towards the South China Sea and the northwestern Pacific Ocean, feeding the monstrous typhoons there.

Ø  The monsoon trough is like a little car trying to cross this busy and wide highway from the Andaman Nicobar Islands to India across the Bay of Bengal.

Conclusion -

This already complicated phenomenon of global warming affecting cyclogenesis adds another complication in the dynamics of Monsoon. Fortunately, a late monsoon onset doesn’t necessarily mean a monsoon deficit. Then again with the looming crisis of EL Nino the nation awaits the best and is preparing for the worst.