Page 544 - AWSAR 2.0

520 || AWSAR Awarded Popular Science Stories - 2019
climate at the Indian Institute of Tropical Meteorology, Pune, under the supervision of Dr. Roxy Mathew Koll and Dr. Medha Deshande. The North Indian Ocean cyclones are the least explored cyclones worldwide. Although some of the deadliest cyclones occurred in this basin, there is still a lack of an understanding of the cyclone mechanism and its characteristics in this part of the world. This gave me an immense opportunitytounderstandthecharacteristicof the cyclones in this basin and how the cyclone characteristics, such as its frequency, track and intensity, would change in the future.
In our research, we explored how the ocean played a role in governing the cyclone frequency and intensity. Further, we also explored how cyclones affected the ocean. We used various observation and reanalysis datasets such as ERA-interim, NCEP- NCAR reanalysis dataset, Joint Typhoon Warning Center Best track dataset, and India Meteorological Department
cyclone e-atlas for analysing the
cyclones and the associated
atmospheric and oceanic
conditions. We observed that
large sea surface temperatures
of the ocean fuelled intense
cyclones in the Arabian Sea
and the Bay of Bengal. Also,
the intense cyclones, after their
formation, cooled the ocean
by 2°C-3°C. The response of
the ocean due to the cyclone
was found to be different
before the monsoon and after
the monsoon. This different
response in the sea surface
temperature cooling was linked to ocean dynamics. We also observed that in the sudden intensification of the very severe cyclones, such as Ockhi that affected Kerala in October 2017 and cyclone Fani that affected Odisha in April 2019, was mainly driven by the large
ocean surface and subsurface temperatures. Overall, there is a rising trend in the intensity of cyclones in the North Indian Ocean. However, we have seen that the cyclones which form in the Bay of Bengal in the month before the southwest monsoon, that is April- May, have shown a decrease in intensity in the recent decade. Nevertheless, the rising trend in the intensity of the cyclones after the monsoon season (October-December) in the Bay of Bengal and before and after the monsoon season (April-May and October-December) in the Arabian Sea is posing a severe risk for the densely populated coastline of India. Not only the local atmospheric and oceanic conditions but also the large scale atmospheric conditions are conducive for the enhanced formation of the cyclones, especially in the Arabian Sea before the monsoon season (month of May). The anomalous cooling of the equatorial Pacific during 1999-2016 has led to favourable atmospheric conditions through teleconnections in the Indo- Pacific region. This has led to enhanced cyclone formation in the Arabian Sea during the
aforementioned period.
Our research will aid
the scientific community in improving an understanding of the role of oceans in the intensity and frequency of cyclones. It is noteworthy that the forecast of the cyclones has increased significantly in recent years; however, still, computer models face the problem in simulating the
intensity. The recent example is the sudden intensification of cyclone Ockhi very close to Kerala coast immediately after its formation. The computer models failed to capture this sudden intensification much in advance, leaving a very little window for the government
The North Indian Ocean cyclones are the least explored cyclones worldwide. Although some of the deadliest cyclones occurred in this basin, there is still a lack of an understanding of the cyclone mechanism and its characteristics in this part of the world.