CYCLONE'S EFFECT ON MONSOON

1. Context

2. Formation of a cyclone

• We are seeing cyclone formations in the premonsoon cyclones season, closer to the monsoon onset, arguably 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 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.

3. Global warming and Monsoon

• A drastic change in the monsoon rainfall intensity, duration, frequency, and spatial distribution can be attributed to Climate Change. However, it is too soon to conclude.
• If all this is in response to global warming then it can be permanent and might accelerate. If not then the monsoon system will revert to a more normal state.
• More data and reanalysis are needed to get a clear picture of the complete separation of the global warming impact from natural climate variability (Such as El Nino).

4. 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 backwinds blowing from the southwest to the northeast can pull the monsoon trough forward, and assist in the monsoon's onset.
• Earlier this year, the Bay of Bengal had Cyclone Mocha develop in the first half of May and 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 backwinds helped the monsoon set in on time over the Andaman and Nicobar Islands.
• 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 1 degree Celsius in the premonsoon season.
• The late-season cyclone Biparjoy is still 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.

5. Impact of Monsoon on India

5.1 Positive

• About 64% of people in India depend on agriculture for their livelihood and agriculture itself is based on monsoon.
• The agricultural prosperity of India depends very much on timely and adequately distributed rainfall. If it fails, agriculture is adversely affected particularly in those regions where means of irrigation are not developed.
• Regional variations in monsoon climate help in growing various types of crops.
• Regional monsoon variation in India is reflected in the vast variety of food, clothes, and house types.
• Monsoon rain help recharge dams and reservoirs, which is further used for the generation of hydroelectric power.
• Winter rainfall by temperate cyclones in north India is highly beneficial for Rabi crops.

5.2 Negative

• The variability of rainfall brings droughts or floods every year in some parts of the country.
• Sudden monsoon burst creates a problem of soil erosion over large areas in India.
• In hilly areas sudden rainfall brings landslides which damage natural and physical infrastructure subsequently disrupting human life economically as well as socially.

6. Cyclones: Mawar, Biparjoy, and Guchol 

• Cyclone Biparjoy is not interacting much with the monsoon trough at this time. However, its late birth, as well as the late onset of the monsoon, are both closely related to typhoons in the northwestern Pacific Ocean.
• On May 19, Typhoon Mawar was born and dissipated by June 3. Mawar qualified as a '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. 
• Tropical storm Guchol is now active just to the east of the Phillippines and is likely to continue northwest before veering off to the northeast. These powerful typhoons are thirsty beasts and demand moisture from far and wind.
• 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.
• Southwesterly winds over the Arabian Sea are welcome news they bring large quantities of moisture onto the Indian subcontinent.
• 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 Southwest.
• 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 northeastward over the Bay, a key reason why the monsoon trough has been struggling to reach Kerala.

Previous year Questions