Browsing by Author "Das, Sushant"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Projected changes in the mean and intra-seasonal variability of the�Indian summer monsoon in the RegCM CORDEX-CORE simulations under higher warming conditions
    (Springer Science and Business Media Deutschland GmbH, 2021) Shahi, Namendra Kumar; Das, Sushant; Ghosh, Soumik; Maharana, Pyarimohan; Rai, Shailendra
    The present study employed the latest high-resolution regional climate model (RegCM4), driven by MPI-ESM-MR boundary conditions from the CORDEX-CORE South Asia framework to investigate the possible projected changes in the mean and intra-seasonal variability of the�Indian summer monsoon (ISM) precipitation and their associated dynamics during near future (NF; 2041�2060) and far future (FF; 2080�2099) with respect to the historical period (1995�2014) under RCP8.5 scenario. Extensive evaluation analysis indicates that the RegCM4 is fairly able to simulate the spatial�temporal distribution of the observed mean and extreme precipitation, low-level jet, and intra-seasonal variability i.e. active and break composite patterns of the precipitation anomalies over India during the historical period. A substantial decline in the projected precipitation during ISM is estimated over central and northwest India in NF (about 10�30%) as well as in FF (upto 50%), which may be attributed to the weakening and northward shift of low-level winds. The occurrences as well as the intensity of the extreme precipitation events are expected to increase over India in the future. The precipitation during the projected active spells will escalate over the monsoon core region. This is supported by the decrease in sea level pressure over land, which favors the winds to transport more moisture from the adjoining seas for the formation of convective clouds, which is partly indicated through the decline in net surface longwave radiation. On the other hand, the precipitation intensity during the projected break spells is expected to further decrease in the future. � 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
  • Thumbnail Image
    Publication
    Signals of northward propagating monsoon intraseasonal oscillations (MISOs) in the RegCM4.7 CORDEX-CORE simulation over South Asia domain
    (Springer Science and Business Media Deutschland GmbH, 2023) Ghosh, Soumik; Miller, Arthur J.; Subramaniam, Aneesh C.; Bhatla, R.; Das, Sushant
    Northward propagating summer monsoon intraseasonal oscillations (MISOs) in the Indian Ocean region remain poorly understood and difficult to predict. Here we examine a free-running high-resolution regional atmospheric model (RegCM4.7 with 25�km resolution), forced distantly at the boundaries by atmospheric observations (ERA-Interim, 0.75?) and forced locally by observed sea-surface temperature (SST) over the period 1979�2016, to assess its ability to reproduce key aspects of these MISOs. We find that the model MISO exhibits spatial structures and northward propagation characteristics broadly similar to observed MISO when confining the analysis to the 25�90 day period band. The MISO precipitation anomalies are then shown to be consistent with previously known observed relationships to broad-scale sea-level pressure patterns, Inter-Tropical Convergence Zone (ITCZ) positioning, and changes in the regional Hadley Cell component. The total simulated seasonal (JJAS) rainfall anomalies over India are not significantly correlated with observations, indicating that intrinsic variations in the regional model atmosphere dominate most of the precipitation variability. However, the bandpass-filtered MISO anomalies surprisingly exhibit a significant correlation (0.61) with observations. This suggests that instabilities in the regional broad-scale atmospheric circulation, e.g., linked to the ITCZ position or strength, may be partly controlled by the large-scale atmospheric flows specified at the domain boundaries and/or that specified local SST anomalies may help to guide some fraction of the developing model MISO to follow observations. This result motivates further research on MISO initiation and development using this type of regional atmospheric model. � 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
  • Thumbnail Image
    Publication
    Will Warming Climate Affect the Characteristics of Summer Monsoon Rainfall and Associated Extremes Over the Gangetic Plains in India?
    (John Wiley and Sons Inc, 2023) Pant, Manas; Bhatla, R.; Ghosh, Soumik; Das, Sushant; Mall, R.K.
    The Indo-Gangetic Plain (IGP) bears great agricultural importance and contributes to a major share of national GDP of India. In present study, a location-specific comprehensive analysis of rainfall extremes over IGP, using second generation CORDEX-CORE simulations in the present and future scenarios (under high emission RCP8.5 scenario) have been performed. Here, the high-resolution CORDEX-CORE simulations with International Centre for Theoretical Physics's regional climate model (RegCM4.7) have been considered for the detailed rainfall characteristics assessment. Twelve thresholds-based climate indices have been analyzed to investigate the characteristics of rainfall extremes during three-time slices: 1986�2005 (historical), 2041�2060 (near future) and 2080�2099 (far future). The RegCM4 projections suggested a substantial decline in mean Indian Summer monsoon rainfall (ISMR) and wet days (rainfall ? 1�mm; 7%�14%) over IGP under high-emission RCP8.5 scenario. The contribution of 90th and 99th percentile days and total�rainfall on wet days, seems to be�get enhanced in future by 14%�35%, which implies the increase and intensification in rainfall extremes over IGP by the end of the 21st century. Further, the decline in ISMR and negligible changes in annual rainfall over IGP suggest the possible shift of monsoon regime during the later months of the year in warming climate. Thus, findings of present study may play a crucial role in predicting the ISMR and rainfall extremes over the IGP. Therefore, it can be useful for scientists and policymakers to plan and implement mitigation strategies. � 2023 The Authors. Earth and Space Science published by Wiley Periodicals LLC on behalf of American Geophysical Union.