Cyclone frequency may rise over Indian coast from the warming of Pacific: study

Syllabus: Disaster and its management

Tropical cyclones that originate near the Equator, while being devastating, have been unusually subdued in recent decades.
Last major cyclone in India was Cyclone Okchi, which devastated parts of Kerala, Tamil Nadu and Sri Lanka in 2017.
A combination of global warming and a cyclical event called the Pacific Decadal Oscillation (PDO) that repeats every 20 to 30 years, could make such cyclones more frequent in the coming years.
The number of such equatorial-origin cyclones was 43% less between 1981 – 10 compared to 1951 – 80, and this was because the PDO was in a ‘warmer’ or positive phase.

ENSO

El Nino: A warming of the Central Equatorial Pacific – reduced rainfall over India
La Nina: cooler than normal temperatures – linked to excessive rainfall.
This pattern is collectively called the El Nino Southern Oscillation (ENSO) phenomenon
repeats in the Pacific over two to seven years.
Positive and negative phase of ENSO can be detected much faster than PDO.
In 2019, the PDO entered a cooler, negative phase and if it remains so, could mean more tropical cyclones in the post-monsoon months that originate near the equator – It’s usually rare for cyclones to form near the Equator but when the waters are warm, they can gain more moisture and rise in intensity.
An El Nino is developing in the Pacific, the effects of which are manifested in central and southern India, which have recorded rainfall deficits of 7% and 17%, respectively.

PDO

PDO: corresponds to a warmer than average Western Pacific Ocean and relatively cooler Eastern Pacific
plays out over much longer time scales.
a ‘positive’ or ‘warmer phase’ of a PDO can be known only after several years of measuring ocean temperatures and their interaction with the atmosphere.

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