Cyclones in the Arabian Sea have been found to make slower progress, attracting as much energy available while at sea and finally turning into monstrous severe intensity cyclones while hitting the coasts.
The Arabian Sea is turning into a perfect ocean basin for the development of cyclones as researchers have noted a 52 per cent rise in the storms here, since 2001.
Moreover, cyclones in the Arabian Sea have been found to make slower progress, attracting as much energy available while at sea and finally turning into monstrous severe intensity cyclones while hitting the coasts.
In May this year, cyclone Tauktae formed close to Lakshadweep, traveled northwards, and hit the Gujarat coast. The storm was so severe, that it retained its intensity for 24-hours post-landfall and brought rain over parts of Rajasthan, Delhi and Uttar Pradesh. Whereas normally cyclones fizzle out upon reaching land.
Climatologically, the North Indian Ocean region — covering the Arabian Sea and the Bay of Bengal — records five cyclones in a year, four of which originate in the latter. May and November remain active months in a year.
However, climate scientists are now observing a departure to this normal, especially in terms of intensity and severity with respect to storms formed over the Arabian Sea during recent decades.
“Earlier, the southwest Indian Ocean region would be cooler. But there is a larger change observed in the sea surface temperatures recorded over the Arabian Sea than what was observed over the Bay of Bengal. In addition, the availability of moisture is much higher in the Arabian Sea whereas the Bay of Bengal appears to be turning moisture-deficit,” said Roxy Mathew Koll, senior scientist at the Indian Institute of Tropical Meteorology (IITM), Pune, who was part of the recent study published in the journal Climate Dynamics by Springer.
A look at the cyclones formed over the Arabian Sea, during the last four years, and their intensities indicate that all of them were of severe cyclones (wind speed 89 – 117 kms /hr) or more. These include Extremely Severe Cyclone Mekanu (2018), Very Severe Storm Vayu (2019), Severe Cyclonic Storm Nisarga (2020) and Very Severe Cyclonic Storm Tauktae (2021). Three of these hit either Gujarat or Maharashtra, indicating growing vulnerabilities of India’s west coast.
In 2019 alone, four cyclones – Vayu, Hikka, Kyarr and Maha originated in the Arabian Sea and remained one of the most active years for storms in the recent past.
Storms intensify and sustain depending on the energy availability through heat load in the oceans and moisture. The study has also highlighted that the accumulated cyclone energy — the total wind energy during the lifespan of a storm, in the Arabian Sea has nearly tripled, indicating the extent of warming the Arabian Sea might have undergone in recent years.
In most storms recorded during 2001 – 2019 in the Arabian Sea, an 80 per cent rise in cyclone’s duration was researchers from Savitribai Phule Pune University, National Institute of Technology-Rourkela and KBC North Maharashtra University, who were part of this joint study.
Overall, November was found to be the most conducive month for cyclogenesis and intensification in both the seas, the study noted.
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