EDITORIAL ANALYSIS : How does a cyclone affect the monsoon’s onset?

Source: The Hindu

Prelims: Current events of national and international importance(cyclone, Monsoons, Pacific ocean, Southern ocean, super cyclonic storm, cyclone Mawar, Biparjoy, and Guchol etc
Mains GS Paper III: Geographical features and their locations- change in critical geographical features etc

ARTICLE HIGHLIGHTS

The impact of global warming on the monsoons are manifest in the onset, withdrawal, its seasonal total rainfall, and its extremes.
India, with nearly 18% of the world’s population, occupies about 4(two point four)% of the total geographical area and consumes 4% of total water resources.

INSIGHTS ON THE ISSUE

Context

Tropical Cyclones:

They are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges.
Tropical Cyclones are one of the most devastating natural calamities in the world.
Tropical cyclones originate and intensify over warm tropical oceans.
The conditions favorable for the formation and intensification of tropical storms are:
- Large sea surface with temperature higher than 27° C.
- Presence of the Coriolis force.
- Small variations in the vertical wind speed.
- A pre-existing weak low- pressure area or low-level-cyclonic circulation.
- Upper divergence above the sea level system.

Nomenclature of Tropical Cyclones:

The process of naming cyclones involves several countries in the region and is done under the aegis of the World Meteorological Organization (WMO).
For the Indian Ocean region, a formula for naming cyclones was agreed upon in 2004.
Eight countries in the region – Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand – all contributed a set of names which are assigned sequentially whenever a cyclonic storm develops.

Climate change and Indian Monsoons:

What does global warming do?

Global warming affects the cyclones over the Indian Ocean and the typhoons over the northwestern Pacific Ocean.

Factors Affecting cyclone and monsoon formation:

cyclone formations in the pre-monsoon cyclone season, closer to the monsoon onset, are due to the influence of a warmer Arctic Ocean on winds over the Arabian Sea.
The monsoon is 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).
- Bridge refers to two faraway regions interacting in the atmosphere while a ‘tunnel’ refers to two remote oceanic regions connecting within the ocean.

Why does a cyclone’s position matter?

Some cyclones in the North Indian Ocean have had both positive and negative impacts on the onset of the monsoon.
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 is concerned.
- The monsoon trough is a low-pressure region that is a characteristic feature 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.

Cyclone Mocha:

It developed in the first half of May and intensified 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.

Cyclone Mawar, Biparjoy, and Guchol:

The late-season cyclone Biparjoy:

It is chugging along in the warm Arabian Sea and may well rapidly intensify – i.e., have its wind speeds increase by 55 kmph within 24 hours – before making landfall.

Cyclone Biparjoy is not interacting much with the monsoon trough at this time.
- Its late birth as well as the late onset of the monsoon are both closely related to typhoons in the northwestern Pacific Ocean.

Typhoon Mawar:

Mawar qualified as a ‘super typhoon’ and is thus far the strongest typhoon to have taken shape in May.
It is the strongest cyclone of 2023 so far.
Mawar pulled winds across the equator into the North Indian Ocean, setting up southwesterly winds over parts of the Arabian Sea and the Bay of Bengal.
- ‘Southwesterly’ means blowing from the southwest.

Tropical storm Guchol:

It is active just to the east of the Philippines and is likely to continue northwest before veering off to the northeast.

Southwesterly winds over the Arabian Sea and Bay of Bengal:

Arabian Sea:They bring large quantities of moisture onto the Indian subcontinent.
Southwesterly winds over the Bay of Bengal:
- 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.

Way Forward

Winds were southwesterly over the entire Bay when Mawar was active.
- This continues to be the case now due to Guchol, which has 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.
The strong southwesterly winds over the Bay of Bengal can be imagined to be a very large highway with heavy traffic 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 complicated dance of global warming affecting cyclogenesis over the Pacific and North Indian Oceans, the warming over the North Indian Ocean and the late pre-monsoon cyclones and typhoons is together just another wrench in the dynamics of the monsoons
- Also in the predictions of the monsoon’s onset and its evolution through the season.
A late monsoon onset does not necessarily indicate a monsoon deficit.
- This year is unique, with an impending El Niño.
The nation waits and watches for the arrival of the monsoon – as always hoping for the best and preparing for the worst.