Browsing by Author "Sanjay Bist"

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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.
Does climate change induce desertification in Gujarat?
(Springer Science and Business Media Deutschland GmbH, 2025) R. Bhatla; Richa S. Singh; Priyanka; R. K. Mall; Sanjay Bist
Land degradation refers to the decline in economic and biological productivity of land caused by climatic variability and human activities, leading to disrupted ecosystem functions. Gujarat, located in the dry and semi-arid region of India, is particularly vulnerable to these processes due to its dependence on monsoon precipitation, which is characterized by significant variability. This study examines rainfall data from the India Meteorological Department for the period 2000 to 2020 and satellite-derived Normalized Difference Vegetation Index (NDVI) values for 2001, 2011, and 2021 to assess spatial and temporal trends in desertification across selected districts. The analysis indicates an overall increasing trend in monsoonal rainfall during the two decades, but this increase is unevenly distributed, with certain districts experiencing more pronounced variability. Remote sensing data reveal a complex pattern of vegetation dynamics. Districts like Porbandar and Bharuch show improvements in NDVI values, suggesting enhanced vegetation cover and potential recovery from land degradation. Conversely, Vadodara exhibits declining NDVI trends, highlighting escalating risks of desertification, likely driven by intensified anthropogenic pressures such as industrialization and deforestation. This research highlights the critical interplay between climatic factors and land use changes in shaping regional ecological health. The findings underscore the need for proactive and region-specific land management strategies to mitigate desertification. With the help of reliance on robust satellite-based monitoring and high-resolution climatic data, this study provides a replicable framework for understanding and combating land degradation in similar vulnerable districts. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Effect of unusual dust event on meteorological parameters & aerosol optical and radiative properties
(India Meteorological Department, 2018) V.K. Soni; Sanjay Bist; R. Bhatla; S.C. Bhan; Gajendra Kumar; M. Sateesh; Siddhartha Singh; D.R. Pattanaik
A very unusual dust plume generated from dust-storm activities over the Arabian Peninsula and Southwest Asia affected the north-west region of India between March 20 and 23, 2012, causing significant reductions in air quality and consequently changes in meteorological parameters. Ground based measurements of aerosol optical depth at 500 nm reached 1.015 ± 0.24 and 0.837 ± 0.042 at Jodhpur while Angstrom exponent dropped to-0.030 and-0.065 on March 20 and 21, 2012 respectively. The AOD reached 0.959 in Delhi while Angstrom exponent dropped to 0.006 on March 21, 2012. PM10 concentration peaked at an unusually high value of more than 1800 μgm-3 during dust storm hours of March 20, 2012 at Delhi. Moderate Resolution Imaging Spectrometer (MODIS) retrieved aerosol optical depth also exhibited high values as well along the path of dust storm and dust plume. The intensity of the dust plume was such that it caused significant cooling at the surface. The large reduction in the radiative flux at the surface level had caused a drop in surface temperature by approximately 2-10 °C. Shortwave and longwave Direct Aerosol Radiative Forcing was calculated using SBDART during the dust period. © 2018, India Meteorological Department. All rights reserved.
Study of surface fluxes during onset of summer monsoon over India
(John Wiley and Sons Ltd, 2016) R. Bhatla; P.V.S. Raju; R.K. Mall; Sanjay Bist
An examination of the variations of surface meteorological fields and derived surface heat fluxes associated with onset of summer monsoon seasons over India based on 50 years data from 1957 to 2006 is carried out over the domain 30°S-30°N and 30°-150°E. Significant changes in the surface meteorological parameters are observed over Arabian Sea off Somali coast, Bay of Bengal and move eastwards to northwards as onset approaches. The changes and shift in the south Indian Ocean are not prominent. Some precursors such as changes in almost all parameters used in this study over northern Australia and its adjoining, and East China Sea during pre- to post-onset phase indicate the approach of onset situation. © 2016 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