01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-05-0320 |
| Title of Abstract | Warming Indian Ocean spinning more cyclones ⿿ A case study from 2019 |
| Authors | Sukumaran Prasanna Kumar*, Jayu Narvekar, Riyanka Roy Chowdhury, Subhra Prakash Dey |
| Organisation | National Institute of Oceanography (NIO) |
| Address | Dona Paula Panaji, Goa, India Pincode: 403004 E-mail: prasanna.ocean@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Tropical cyclones occur twice in the North Indian Ocean (NIO) - during spring-summer and fall-winter transitions. In recent years, there has been a noticeable increase in cyclone activity across the NIO, which has been linked to climate warming. The year 2019 was particularly remarkable, producing eight cyclones that ranged in intensity from cyclonic storms to super cyclones. Of these, five cyclones formed in the Arabian Sea (AS) and three in the Bay of Bengal (BoB). This was an unprecedented event for two key reasons - the total number of cyclones in the AS was the highest since 1960, and significantly out-numbered those in the BoB. An analysis of long-term ocean-atmosphere parameters revealed that in 2019, the ocean and atmospheric conditions aligned to create favorable dynamic and thermodynamic environments necessary for cyclone formation. Observations from satellite and in situ data showed significant variability in the upper ocean's physical and biogeochemical responses to the cyclones. The cyclone-induced changes in the AS such as surface cooling, increased chlorophyll biomass, enhanced primary productivity, and elevated CO⿿ outgassing were much more pronounced than those in the BoB. This contrasting response was attributed to differences in upper ocean stratification and wind stress curl between the two basins. Specifically, reduced upper ocean stability and stronger wind-driven Ekman suction in the AS in 2019 contributed to the more intense oceanic response. Two major atmospheric and oceanic contributors to the formation of five cyclones in the AS during 2019 were the highest mid-tropospheric relative humidity and the second-highest upper ocean heat content recorded since 2000. The anomalously high cyclone activity in the NIO in 2019 was driven by a combination of factors, rapid warming of the western Indian Ocean, a strong Indian Ocean Dipole (IOD) event, and changes in the Walker circulation associated with the IOD. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Tropical cyclone, Sea surface temperature, Relative humidity, wind, chlorophyll a, Carbon dioxide |
| For Awards | no |