PANJIM: The total time spent by the Biparjoy cyclone on the ocean starting from its formation to landfall in Gujarat lasted for 10 days and 18 hours, which is the longest ever in the Arabian Sea. The previous longest duration was cyclone Kyarr in the Arabian Sea in October 2019, which lasted for 9 days and 15 hours, former director of National Institute of Oceanography (NIO), Dr S Prasanna Kumar said.
This shows that the duration of cyclones from genesis to landfall is increasing, posing a huge threat not only to the inhabitants on the west coast but also to agriculture.
“Generally, the average duration of a cyclone is usually three to four days. The Biparjoy cyclone duration was for 10 days. While the previous longest duration of cyclones were cyclone Kyarr, 9 days and 15 hours, Maha (in 2019), 9 days and 12 hours and Fani (2019) 8 days and 12 hours. Usually, the average length of a cyclone is four to five says. This shows that the length of the cyclone duration is increasing,” Dr Prasanna Kumar told O Heraldo.
“This means that the more time a cyclone stays in the ocean, it acquires more energy from the ocean. Due to this, the damage caused will be much more. Not only will there be a direct threat to living beings, but also to agriculture. In Goa for example, we have khazan lands. So, more cyclones, with longer durations mean that more flooding and increase in salinity of the fields. This will have a drastic impact on paddy cultivation,” he said.
In fact in a study on cyclone trends in India between 1960 and 2022 done by Dr Prasanna Kumar along with R S Abhinav and Dr Jayu Narvekar from NIO, and Evelin Francis from Vikram Sarabhai Space Centre, Thiruvananthapuram, Kerala, it has been found that in the Arabian Sea, until 1995 the cyclone occurrence was very rare.
“The cyclones in the Arabian Sea are increasing due to the warming of the ocean. In 2019 there were five cyclones on the west coast, against the normal of one per year. This was the maximum number of cyclonic disturbances observed in the Arabian Sea,” the former NIO director said.
In comparison, the Bay of Bengal witnessed only three cyclones in 2019, against the normal of four per year.
There are mainly five categories of cyclonic storm defined by the India Meteorological Department (IMD). (1) Cyclonic Storm with wind speed of 62-87 km per hour, (2) Severe Cyclonic Storm (88-117 km/hr), (3) Very Severe Cyclonic storm (118-167 km/hr), (4) Extremely Severe Cyclonic Storm (168- 221km/hr) and (5) Super Cyclonic Storm (222 km/hr and higher).
“We have found that every decade, there has been an upward trend in cyclones. More importantly, the category of cyclones is changing. Arabian Sea is witnessing a higher category of cyclones. Category four cyclones (extremely severe cyclonic storm) never occurred on the Arabian Sea before 2000. But now it is happening,” he said.
This is happening because after 1995, the rate of warming in the Arabian Sea has increased due to global climate change.
“Whenever the ocean becomes very warm, it will spin the cyclone to cool it down. The heating pattern of the ocean is changing. As the carbon dioxide in the atmosphere is increasing, the temperatures are also rising. Also, land use patterns have a bearing. Forests are getting cleared and converted into agriculture lands, agriculture land is getting used for urbanisation and dwelling. So, when the vegetation cover is altered, the amount of radiation retained by the ocean also is more. This is causing havoc,” he said.
“We are also seeing an increase in the occurrence of cyclones before the onset of monsoon, thus delaying the rains. This means the sowing for kharif crops will also get affected, apart from a longer period of water shortage. Authorities from all departments now have to have a synergetic plan on dealing with the impacts of extreme weather events caused by climate change,” he added.