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<p>Monsoon systems play a pivotal role in shaping the hydrological landscape of the Indian Subcontinent, influencing the livelihoods of over a billion people through their profound impact on rainfall distribution. This study is conducted on an extensive assessment of extreme precipitation, precipitation trends, and its influencing factors spanning 41 years (1979–2019) within these monsoon systems, utilizing fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5). This comprehensive diagnostic study aims to understand the complex mechanisms underlying Monsson Low-Pressure Systems (MLPSs) and how they are directly related to rainfall events associated with the monsoon. The paper outlines the complex function of these monsoon systems in regulating intense precipitation occurrences in the Indian Subcontinent. The study looks into the main variables influencing MLPSs-related changes in rainfall patterns. It aims to unravel the complex relationship between these systems and the erratic but essential precipitation events that they set off. With the study of 252 monsoon depressions and 305 monsoon lows, our findings reveal distinct trends in rain rates within specific quadrants of monsoon depressions and lows. Notably, there has been an increase in precipitation rates observed in the southwest quadrant of the vortex center. In contrast, the eastern quadrants experienced a decline in precipitation in case of monsoon depression. However, in the case of lows, this pattern is different. This study also analyzes the influencing factors associated with rainfall and their correlation with rainfall.</p> Graphical Abstract <p>This graphical abstract visually summarizes a 41-year (1979–2019) diagnostic study on monsoon low-pressure systems (MLPSs) and their influence on rainfall across the Indian Subcontinent, utilizing ERA5 reanalysis data. The left panel displays a hexbin map of monsoon depressions, and the right panel shows monsoon lows, indicating the frequency of occurrence. Six subplots between the maps depict vortex-centered rainfall composites (mm/day) for monsoon depressions and lows across June, July, August, and September (JJAS). For monsoon depressions, precipitation rates in the southwest quadrant increased by 6&#xa0;mm/day/decade (95% confidence level), while northern sectors show a slight decline (not significant). Monsoon lows exhibit a smaller increase of 3&#xa0;mm/day/decade in the northwest quadrant, with a minor decrease in the southwest (not significant). The bottom panels present a time series of precipitation rates with red and blue lines showing annual variability and trends, respectively, with a yellow text box noting an increase in precipitation rates in the southwest quadrant of the vortex center. In this core finding, depressions show a significant upward trend and lows a broader but less intense pattern. Here, upward arrows denote increasing trends and downward arrows denote decreasing trends in frequency and intensity of these systems.</p> <p></p>

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Diagnostic Study of Monsoon-Linked Rainfall Events: Unraveling the Role of Monsoon Low Pressure Systems across the Indian Subcontinent

  • 期刊论文

  • 发表日期：

    2025年7月9日

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  • Nitin Lohan,
  • D. R. Pattanaik,
  • Sushil Kumar,
  • R. K. Giri

摘要

Monsoon systems play a pivotal role in shaping the hydrological landscape of the Indian Subcontinent, influencing the livelihoods of over a billion people through their profound impact on rainfall distribution. This study is conducted on an extensive assessment of extreme precipitation, precipitation trends, and its influencing factors spanning 41 years (1979–2019) within these monsoon systems, utilizing fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5). This comprehensive diagnostic study aims to understand the complex mechanisms underlying Monsson Low-Pressure Systems (MLPSs) and how they are directly related to rainfall events associated with the monsoon. The paper outlines the complex function of these monsoon systems in regulating intense precipitation occurrences in the Indian Subcontinent. The study looks into the main variables influencing MLPSs-related changes in rainfall patterns. It aims to unravel the complex relationship between these systems and the erratic but essential precipitation events that they set off. With the study of 252 monsoon depressions and 305 monsoon lows, our findings reveal distinct trends in rain rates within specific quadrants of monsoon depressions and lows. Notably, there has been an increase in precipitation rates observed in the southwest quadrant of the vortex center. In contrast, the eastern quadrants experienced a decline in precipitation in case of monsoon depression. However, in the case of lows, this pattern is different. This study also analyzes the influencing factors associated with rainfall and their correlation with rainfall.

Graphical Abstract

This graphical abstract visually summarizes a 41-year (1979–2019) diagnostic study on monsoon low-pressure systems (MLPSs) and their influence on rainfall across the Indian Subcontinent, utilizing ERA5 reanalysis data. The left panel displays a hexbin map of monsoon depressions, and the right panel shows monsoon lows, indicating the frequency of occurrence. Six subplots between the maps depict vortex-centered rainfall composites (mm/day) for monsoon depressions and lows across June, July, August, and September (JJAS). For monsoon depressions, precipitation rates in the southwest quadrant increased by 6 mm/day/decade (95% confidence level), while northern sectors show a slight decline (not significant). Monsoon lows exhibit a smaller increase of 3 mm/day/decade in the northwest quadrant, with a minor decrease in the southwest (not significant). The bottom panels present a time series of precipitation rates with red and blue lines showing annual variability and trends, respectively, with a yellow text box noting an increase in precipitation rates in the southwest quadrant of the vortex center. In this core finding, depressions show a significant upward trend and lows a broader but less intense pattern. Here, upward arrows denote increasing trends and downward arrows denote decreasing trends in frequency and intensity of these systems.