Browsing by Author "Aditya Kumar Dubey"

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Comparative changes in seasonal marine heatwaves and cold spells over the Tropical Indian Ocean during recent decades and disentangling the drivers of highly intense events
(John Wiley and Sons Ltd, 2023) Anand Singh Dinesh; Alok Kumar Mishra; Aditya Kumar Dubey; Suruchi Kumari; Akash Anand
The unprecedented increase in the Sea Surface Temperature (SST) in the warming climate yield stress to the system and pose severe threats to the marine ecosystem. Marine Heatwaves (MHWs) and Marine Cold Spells (MCSs) are two extreme events related to SST variability. For better management of ocean productivity, marine ecosystem, marine services, and fisheries, the understanding of seasonal discrepancies rather than annual documentation of MHWs and MCSs metrics is more utilitarian. This study documents the decadal changes in the MHWs and MCSs over the Tropical Indian Ocean (TIO) for all seasons. Additionally, highly intense events (based on intensity and duration) are identified and demonstrate the associated drivers. During the past two decades (1982–1990, 1991–2000), the MCSs were more frequent than MHWs in every season. However, in the recent two decades (2001–2010, 2011–2020), TIO become more prone to MHWs with considerably more frequent and prolonged events in JJAS months. Moreover, MCSs are disappearing from the TIO. It was noted that the choice of baseline period has an impact on the magnitude of MHWs and MCSs changes, but the spatial pattern (regions with high/low magnitude MHWs and MCSs) stays fairly constant in all baseline period sensitivity checks. The investigation of highly intense events reveals that MHWs and MCSs are produced and sustained by the same drivers when they are at their opposing edges. In general, the coherence effort from winds, net heat fluxes (shortwave radiation, longwave radiation, latent heat flux, and sensible heat flux), mixed level depth, and mean sea level pressure contribute to the genesis of seasonal MHWs or MCSs events. Additionally, in some cases, a single driver (e.g., wind) may also play a crucial role in these extreme events. The remote climate modes of variability, such as El Niño–Southern Oscillation, also contribute significantly to the MHWs and MCSs. El Niño (La Niña) events not only increase the spatial coverage of MHWs (MCSs) but also increases the intensity. © 2023 Royal Meteorological Society.
Heatwaves Over the Indian Subcontinent: Mechanisms, Variability and Sources
(Springer Science and Business Media Deutschland GmbH, 2025) Priyanshu Gupta; Aditya Kumar Dubey; R. Bhatla; Swagata Payra; Sunita Verma
Heatwaves, an extreme temperature events, have gained copious attention. This study conducts a comprehensive analysis of heatwaves (HWs) over four decades from 1980 to 2021. Empirical Orthogonal Function (EOF) analysis is used to identify the dominant spatial pattern in maximum temperature (Tmax) variability across the Indian region. The analysis identifies four significant regions: Central Northeast (CNE), South Central (SC), Northwest (NW) and Southeast (SE) with distinct temperature pattern. Subsequently, the spatial and temporal variations in HWs, indicate an increase in frequency, severity, and duration over the past four decades. Temporal trend shows an increase in HW frequency and duration across most of the regions over a 42-year period. To comprehend the underlying mechanism of HW events, study investigates various meteorological parameters observed during HW days. Maximum temperature anomalies increase by 4–5 °C, accompanied by positive surface solar radiation (SSR) of 10–20 W/m2 along with lower mean sea level pressure (mslp), and a reduction in relative humidity (RH) of − 6% to -15%. Geopotential height at different pressure level highlight anticyclonic circulation pattern associated with temperature extremes. Additionally, backward trajectory analysis is used to delineate distinct source regions and atmospheric processes linked with HW events in different parts of India. A detailed analysis of spatial and temporal variation of HWs and their associated meteorological factors contribute in development of effective mitigation and adaptation strategies. © King Abdulaziz University and Springer Nature Switzerland AG 2025.