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| Abstract Submission No. | ABS-2022-14-0322 |
| Title of Abstract | Upper-ocean responses induced by Cyclone Ockhi (2017) at rapidly intensified and weakened regions: A Case Study. |
| Authors | Jyothi lingala*, Sudheer Joseph, Suneetha P, Matthew Huber |
| Organisation | ESSO - Indian National Centre for Ocean Information Services |
| Address | ESSO - Indian National Centre for Ocean Information Services, Pragati Nagar Hyderabad, Telangana, India Pincode: 500090 Mobile: 9676077530 E-mail: jyothi.l@incois.gov.in |
| Country | India |
| Presentation | Oral |
| Abstract | This study analyzes the influence of upper-ocean stratification in two regions where Rapid intensification and Rapid Weakening of Tropical Cyclone Ockhi (2017) took place. This analysis is performed using simulations from the high-resolution HYbrid Coordinate Ocean Model (HYCOM). Results indicate that oceanic conditions prior to the occurrence of rapid intensification are warmer and fresher while they are relatively cooler and saltier in the rapid weakening region. Analysis of the sea surface temperature anomaly associated with Ockhi⿿s passing showed a weaker cooling when rapid intensification occurred (-0.8C) and larger cooling (-1.9C) when rapid weakening occurred. A detailed examination of the mixed layer heat budget terms revealed the total temperature tendency under rapid intensification was driven roughly equally by surface thermal forcing (-0.01C) and entrainment (-0.0098C); while the tendency in the rapid weakening region was mainly dominated by entrainment (-0.02C). In both of these cases, the role of horizontal advection was minimal towards the total thermal changes. The difference in the magnitude of entrainment-based cooling is mainly attributed to stronger stratification in the rapid intensification regime and weaker stratification in the rapid weakening regime. The strong wind-induced mixing over a weakly stratified ocean resulted in a large drop of dynamic temperature (Tdy) at a rapid weakening regime compared to the intensification regime indicating the prominence of salinity stratification in modulating the ocean⿿s negative feedback to the TC intensity changes. Further, the difference between the depths of mixing length and 26C isotherm at rapid intensification and rapid weakening regimes suggests the incorporation of Tdy instead of Tropical Cyclone Heat Potential in the forecast models, particularly in the salinity stratified regions. |