Biporjoy is part of a new trend in Indian cyclones

Subject :Geography

Section: Physical geography (Climatology)

Context:

The cyclonic disturbances over the North Indian Ocean, which includes the Arabian Sea, the Bay of Bengal and the land area in between, have gone through many significant changes in recent decades.

Details:

The number of cyclonic disturbances in the North Indian Ocean has declined considerably over the past four decades.
- This decline was mostly due to a rapid decrease in the number of cyclonic disturbances originating from the Bay of Bengal, the source of most past cyclones to have made landfall in southeast and west Asia.
- In contrast, the number of such disturbances originating from the Arabian Sea has been steadily increasing in recent years, though the count is still relatively low.
While the frequency of disturbances has decreased, the intensity of cyclones has increased in recent decades.

Why is frequency increasing in Arabian sea?

Cyclone Kyarr and Maha in 2019 were extremely severe on the western coast.
Increased carbon emissions have led to the warming up of Arabian Sea waters.
The more enclosed nature of the sea is promoting more evaporation and cloud formation activities.
Anthropogenic emissions of aerosols have increased six-fold since the 1930s, leading to a weakening of the southwesterly lower-level and easterly upper-level winds that define the monsoonal circulation over the Arabian Sea.
Indian Ocean Dipole which is an irregular natural oscillation of Sea Surface Temperatures (SSTs) in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean-strongest IOD in 60 years.
The increase in the frequency of cyclones over the Arabian Sea has not posed a corresponding increase in the coastal vulnerability along the west coast since most of such cyclones forming over the Arabian Sea were making landfall over the coasts of Oman, Yemen etc. and hence the threat to Gujarat & Maharashtra coasts remains same.