Browsing by Author "Aashna Verma"

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A long-term drought assessment over India using CMIP6 framework: present and future perspectives
(India Meteorological Department, 2023) Aashna Verma; Akash Vishwakarma; Sanjay Bist; Sushil Kumar; R. Bhatla
Research on the characteristics and spread of droughts has progressed significantly for future climate scenarios. However, studies on drought mitigation in relation to climate change have been largely inadequate. This study focuses on the severity and frequency of drought events based on meteorological properties of drought under two climate change scenarios: Shared Socioeconomic Pathway (SSP2 4.5 and SSP5 8.5). We utilized the Sixth International Coupled Model Inter-comparison Project sixth phase (CMIP6) ensemble General Circulation Models (GCMs) to collect historical (1901-2014) and future (2025-2100) precipitation data. IMD gridded precipitation was used as a reference data for comparative studies. We constructed the Standardized Precipitation Index (SPI) under two different Socioeconomic Shared Pathways (SSPs) to analyze future drought scenarios in the Indian region. Our results show a gradual increase in SPI values for future years, indicating an increase in the severity of drought events in the Indian region. The increase is more pronounced under the SSP5 8.5 scenario, which assumes high greenhouse gas emissions and limited climate change mitigation efforts. Furthermore, our results suggest that major dry spells are likely to occur in the first half of the future period, particularly in the case of ACCESS-ESM, one of the GCMs used in our analysis. In contrast, the NOR-ESM-MM model indicates that dry spells are anticipated throughout the entire future period. Overall, our study provides valuable insights into the potential impacts of climate change on drought events in the Indian region. © 2023, India Meteorological Department. All rights reserved.
India's Drought Challenge: Insights From CMIP6 Models on Historical and Future Climate Scenarios
(John Wiley and Sons Ltd, 2025) R. Bhatla; Aashna Verma; Akash Vishwakarma; R. K. Mall
Droughts, wielding devastating impacts on India, serve as the focal point of this research paper that explores key facets of India and its six distinct homogeneous regions' future climate by investigating the frequency, intensity, and underlying mechanisms of droughts. Utilising 10 General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6), spanning 1901 to 2014, our study employs a Multi-Model Ensemble (MME) approach under Shared Socioeconomic Pathways: SSP245 and SSP585 scenarios for the near (2031–2060) and far (2071–2100) future. Examining historical and projected scenarios, our findings reveal shifting patterns in drought frequency and intensity across regions, identifying North-west India (NWI) and North-central India (NCI) as potential hotspots. The study delves into atmospheric dynamics, revealing their role in drought vulnerabilities. Future trends under SSP245 and SSP585 trajectories underscore the impact of anthropogenic activities, with SSP585 projecting heightened drought risks, especially in NWI and NCI. The analysis of atmospheric physics uncovers the influence of moisture, convective processes, and regional climatic factors, attributing intensified drought risks to amplified atmospheric instability, particularly in NWI. Near-future precipitation patterns reflect regional nuances driven by atmospheric physics and climatic factors. Transitioning to the far future reveals persistent precipitation patterns, emphasising the role of emission trajectories in shaping drought conditions. Statistical analyses indicate an increase in drought intensity and duration, with NWI witnessing the maximum number of extreme droughts. Divergent regional patterns necessitate planned, adaptive policies to address evolving climate dynamics. © 2025 Royal Meteorological Society.
The dynamical influence of energy fluxes in modulating variability of the Indian summer monsoon
(Elsevier Ltd, 2025) R. Bhatla; Archana Maurya; Aashna Verma; R. K. Mall; Sanjay Bist
The surface heat fluxes have a significant role in shaping the Indian summer monsoon (ISM) dynamics. The present study investigates the climatological tricadal and decadal variability of surface energy fluxes viz., net shortwave radiation flux, latent heat flux (LHF) and net heat flux (NHF) during ISM season. For that purpose, a long-term (1961–2020) reanalysis data sets derived from the European Centre for Medium-Range Weather Forecasts fifth-generation (ERA5) and National Center for Environmental Prediction-National Centre for Atmospheric Research reanalysis (NCEP-NCAR) has been considered. Significant regional differences and changing patterns have been observed in the distribution of energy fluxes over southern peninsular India, Arabian Sea (AS), Bay of Bengal (BoB), Equatorial Indian Ocean (EIO), and Southern Indian Ocean. The BoB and AS emerge as vital moisture sources, directly contributing to the monsoon rainfall over eastern, central and western India, respectively. A significant positive change in LHF is observed over AS (9W/m2) and EIO (12W/m2) regions, whereas over the BoB region, a negative departure of −8 W/m2 has been persistent in the recent tricade. These changes correspond to the significant negative anomalous patterns of NHF, i.e., −11 W/m2 over AS and −18 W/m2 over EIO, alongside the highest increase in NHF value over the BoB regions (20 W/m2). The pronounced tricadal phase shift of surface fluxes over AS, EIO, and BoB is identified as a contributing factor influencing ISM rainfall. © 2025 Elsevier Ltd