Journal Articles
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Item Intensification of pre-monsoon cyclone: Insights from spring snowmelt discharge /(Research Square, 2024-11-11) Patnaik, KVKRK; Ganapathi, P.The intensification of pre-monsoon cyclones in the northern Bay of Bengal, particularly Cyclones Yaas (2021), is increasingly attributed to the rising influx of snowmelt water from the Ganges and Brahmaputra rivers. Cyclone Yaas intensified over high sea surface temperatures (31.5 to 32°C) and significant freshwater discharge, leading to notable stratification and increased ocean heat content in the upper layers. As Yaas moved through a warm core eddy, the sinking of water caused the isotherms to deepen by 25–50 meters, a process that was further intensified by freshwater discharge due to spring snowmelt. Key ocean heat content in the top 30-meter layer was critical during Yaas's formation, with total incoming shortwave radiation of 420 W/m² and net radiation of 390 W/m² closely aligning with the heat content of 400 W/m² in the central and western Bay, providing the necessary energy for intensification. This study employs integrated datasets, including in situ observations, ERA5-based freshwater flux analysis, and high-resolution numerical simulations, to reveal cyclone-ocean interactions. Findings indicate that similar snowmelt dynamics contributed to the intensification of recent cyclones. With the rising temperatures due to global warming, even minor changes in increasing snowmelt and surface runoff can significantly affect upper ocean dynamics. This highlights the critical role of pre-monsoon freshwater discharge in strengthening cyclones and emphasises the need for better prediction models to understand future cyclone behavior, which can help reduce risks in this vulnerable region. Additionally, in terms of biological processes, the increased fresh water discharge during spring in the northern Bay of Bengal caused high stratification and intense downwelling, which suppressed nutrient-rich subsurface waters and resulted in limited chlorophyll concentrations (1 mg/m³) along Yaas's track, despite phytoplankton blooms in regions of high wind stress.Item The intrusion of spicy water favours the intensification of Arabian Sea cyclones(Taylor & Francis, 2023-03-15) Maneesha, K.; Brahmananda Rao, V.; Patnaik, K. V. K. R. K.; Franchito, S. H.The intensity of the cyclones in the Arabian Sea has been increasing in recent years. Approximately ten storms were intensified into severe cyclones over spicy waters of the northern Arabian Sea during 1998-2019. Reduction in upwelling was observed due to decreasing wind speed, which raised the sea surface temperature (SST) and the intrusion of spicy waters from the Red Sea and the Persian Gulf acted as a barrier to mixing in the top layers, especially in May. Consequently, there was a noticeable increase in the heat content of the 50 m surface layer. This research presents two main rationales that explain the intensification of these cyclones. The first rationale explores the increasing trends in SST and ocean internal energy, while the second investigates the influence of the intrusion of spicy Persian Gulf waters into the Oman coast. The results showed that spicy water from the north suppressed the upwelling in the cold core eddy off the Oman coast and that higher SSTs and high latent heat flux almost double the climatological values off the Oman coast in May.