How does cyclone formation impacts monsoon?
The impact of global warming on the monsoons are manifest in its onset, withdrawal, seasonal total rainfall, and extremes.
Global warming also affects the cyclones over the Indian Ocean and the typhoons over the northwestern Pacific Ocean.
We are seeing cyclone formations in the pre-monsoon cyclone season, closer to the monsoon onset.
How does cyclone formation impacts monsoon?
This is due to the influence of a warmer Arctic Ocean on the winds over the Arabian Sea.
The monsoon is of course also affected by:
The three tropical oceans — Indian, Atlantic, and Pacific;
The ‘atmospheric bridge’ from the Arctic;
The oceanic tunnel as well as the atmospheric bridge from the Southern Ocean (a.k.a. the Antarctic Ocean).
NB: A ‘bridge’ refers to two faraway regions interacting in the atmosphere while a ‘tunnel’ refers to two remote oceanic regions connecting within the ocean.
How does cyclone formation impacts monsoon?
Cyclone Position and Its Importance:
Some cyclones in the North Indian Ocean have had both positive and negative impacts on the onset of the monsoon.
Since cyclonic winds circulate counterclockwisein Northern Hemisphere , the location of a cyclone plays a crucial role in influencing the transition of the monsoon trough.
Monsoon trough is a low-pressure region characteristic of the monsoons.
For example, 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.
Recent cyclones:
Cyclone Mocha (May 2023)
Intensify briefly into a ‘super cyclonic storm’, before weakening rapidly upon landfall.
Mocha’s northwest to east trajectory over the Bay was the result of unusual anticyclones (which rotate clockwise) that have been parked over the Arabian Sea and the Bay of Bengal since March.
Mocha dissipated on May 15 and the back-winds helped the monsoon set in on time over the Andaman and Nicobar Islands.
1. Cyclone Mocha (May 2023)
One severe consequence of the anomalous anticyclones since March is that both the Arabian Sea and the Bay of Bengal have warmed by more than 1º C in the pre-monsoon season.
2. Cyclone Biparjoy (June 2023)
Cyclone Biparjoy is not interacting much with the monsoon trough at this time.
However, it's late birth as well as the late onset of the monsoon are both closely related to typhoons in the northwestern Pacific Ocean.
3. Typhoon Mawar (May 2023)
May 19 - June 3.
‘Super typhoon’ and is thus far the strongest typhoon to have taken shape in May.
It is also the strongest cyclone of 2023 so far.
Mawar pulled winds across the equator into the North Indian Ocean.
Setting up southwesterly winds (blowing from the southwest) over parts of the Arabian Sea and the Bay of Bengal.
3. Typhoon Mawar (May 2023)
Southwesterly winds over the Arabian Sea are welcome news: they bring large quantities of moisture onto the Indian subcontinent.
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.
Winds were southwesterly over the entire Bay when Mawar was active.
5. Tropical storm Guchol
It is now active just to the east of the Philippines and is likely to continue northwest before veering off to the northeast.
These powerful typhoons demand moisture from far and wide.
It become a ‘severe tropical storm’ now.
Winds have been blowing strongly towards the northeastward over the Bay, a key reason why the monsoon trough has been struggling to reach Kerala.
Concerns
The strong southwesterly winds over the Bay of Bengal heading from the southwest, over southern peninsular India and Sri Lanka, towards the South China Sea and the northwestern Pacific Ocean, feeding the monstrous typhoons there.
The monsoon trough in the meantime trying to cross this busy and wide situation from the Andaman Nicobar Islands to mainland India across the Bay of Bengal.
The intricate interplay between global warming, cyclogenesis, and typhoon activity in the Pacific and North Indian Oceans presents challenges in accurately predicting the monsoon onset and its evolution.
The monsoon trough, once considered a reliable system, is now subject to the uncertainties of climate change.
However, a late monsoon onset does not necessarily indicate a deficit in rainfall, although this year's impending El Niño adds further complexity.
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