Intensive cyclones due to warmer sea temperature: IITM study
Pune:Warmer sea surface temperatures (SST) and subsurface temperatures are responsible for the rapid intensification of cyclones that India has witnessed in the recent past, revealed research done by scientists at Indian Institute of Tropical Meteorology (IITM).
Recently, we have seen that in the Arabian Sea and the Bay of Bengal, the temperature of the ocean has been warmer, said scientists.
The paper was recently published in Scientific Reports, published by Nature.
Scientists Vineet Kumar Singh, MK Roxy and Medha Deshpande were part of the study.
The paper stated that the north Indian Ocean, including the Arabian Sea and the Bay of Bengal, accounts for about 6% of the global tropical cyclones.
Speaking about the study, Vineet Kumar Singh, scientist at IITM who also worked on the paper, said that ocean surface temperatures have been warmer than normal.
“The sea temperature has been around 30 degrees Celsius which is warmer than normal. This warm water further fuels the intensification of cyclones. Cyclone Fani which hit the coast of Orissa and intensified in the Bay of Bengal had a lifespan of eight days. On an average, cyclones have a lifespan of four days. This increased time span is due to the warmer SST. We have seen recently that the Bay of Bengal and Arabian Sea, both are experiencing record warm sea surface temperature. High SST provides more energy to cyclones,” said Singh.
In recent years, India has seen super cyclones like Maha, Amphan and Nisarga. Scientists are now attributing the intensity of these cyclones to the warmer SST. Even on the coast of Maharashtra, cyclone Nisarga was seen to intensify in just 24 hours.
“In the future as well, we are likely to witness more such cyclones as the SST and sub-surface temperatures are warmer. Though, the number of cyclones that India experiences every year may not increase, but their intensity will certainly see an increase. This can be harmful for life and property along the coast,” said Singh.
The cyclone frequency in this region varies between one and three in the pre-monsoon (March–May), to two to five cyclones in the post-monsoon (October–December) season. Studies show that there is an increase in the intensity of pre-monsoon cyclones in the Bay of Bengal during recent decades.
He further added that multiple studies across the world have reflected that high SST fuels the cyclones.
Singh further said that Arabian Sea, earlier, had less conducive conditions for cyclones.
“But, in the last 10 years, there are more cyclones in the Arabian Sea. Due to the rotation axis of the Earth, the cyclones tend to take a path towards the Yemen and Oman coast. Nonetheless, their intensity and frequency has increased. Nisarga is one such example which hit the coast of Maharashtra and Gujarat in 2020,” Singh added.
What the study claims
*Cyclone Fani is the strongest pre-monsoon cyclone to form in the Bay of Bengal after 1994.
*This is the second fastest rapid intensification in 24 hours among all the pre-monsoon cyclones in the Bay of Bengal during the period 1990–2019.
*Cyclone Fani is the strongest pre-monsoon (March–May) Bay of Bengal cyclone after 1994.
*The average SST prior to the genesis of cyclone Fani was 30.4 °C. This is the highest SST observed at the genesis centre prior to genesis of any cyclone in April in the Bay of Bengal during the period 1990–2019.
Source: Scientific Reports, Nature
The National Oceanic and Atmospheric Administration (NOAA) which is based in the USA noted that the January global land and ocean surface temperature were 0.80 of a degree Celsius warmer than normal. This makes January the seventh warmest January in the 142-year climate record for earth.