Abstract This study examines the variability in drop size distribution (DSD) of rainfall over Pune from 2018 to 2022, specifically during the months of June to September, using a laser-optical disdrometer. Significant annual and monthly variations in rainfall totals and droplet diameters were observed, with 2019 recording the highest rainfall at 998.44 mm. The analysis consistently shows that smaller raindrops are more numerous, with the highest concentration found for diameters just below 1 mm. Notably, June and September exhibit the largest droplet sizes for high-intensity rainfall events (>50 mm/hr), while July and August have a more consistent droplet diameter range of 0–5 mm, with a peak concentration of smaller droplets (<2 mm). This study underscores the importance of understanding DSD variability to enhance radar-based rainfall estimation and hydrological modelling. A comparison between 2019 and 2020 reveals that the reduction in pollution and changes in atmospheric conditions during the COVID-19 pandemic likely influenced raindrop formation processes. Specifically, 2020 shows a slightly higher concentration of larger droplets compared to 2019. Additionally, rainfall with lower intensity (5 mm/hr) in both years exhibits higher droplets, with the concentration decreasing as intensity increases. Reduced aerosol concentrations are likely responsible for fewer cloud condensation nuclei, resulting in larger cloud droplets and altered rainfall distribution. These changes in the microphysical properties of rain have significant implications for water resource management and flood prediction during extreme weather events. Overall, this study provides valuable insights into the environmental impact of human activities and highlights the interconnection between air quality and precipitation, contributing to improved weather forecasting accuracy and the development of more effective hydrological models. Research highlights <UnorderedList Mark="Bullet"> <ItemContent> Smaller raindrops (1 mm) consistently dominate the drop size distribution over Pune during all monsoon seasons (2018–2022). </ItemContent> <ItemContent> June and September exhibit larger droplet sizes during high-intensity rainfall (50 mm/hr), while July–August show stable microphysical characteristics. </ItemContent> <ItemContent> The monthly variation of b with higher values in September and moderate values in June points to a seasonal shift from convective to stratiform precipitation regimes. </ItemContent> <ItemContent> The COVID-19 lockdown year (2020) shows a relative increase in larger raindrops at moderate to high intensities due to reduced aerosol loading. </ItemContent> </UnorderedList>

Investigating raindrop size distribution and intensity patterns using disdrometer observations over Pune, India

期刊论文
发表日期：

2026年1月3日

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Mrunal Naik,
Nayan Talmale,
Sonali Shete,
Snehal Ghadge,
Shweta Mukim,
Sunil M Sonbawne,
Pradeep Kumar Pallath,
Rohini Lakshman Bhawar

摘要

Abstract

This study examines the variability in drop size distribution (DSD) of rainfall over Pune from 2018 to 2022, specifically during the months of June to September, using a laser-optical disdrometer. Significant annual and monthly variations in rainfall totals and droplet diameters were observed, with 2019 recording the highest rainfall at 998.44 mm. The analysis consistently shows that smaller raindrops are more numerous, with the highest concentration found for diameters just below 1 mm. Notably, June and September exhibit the largest droplet sizes for high-intensity rainfall events (>50 mm/hr), while July and August have a more consistent droplet diameter range of 0–5 mm, with a peak concentration of smaller droplets (<2 mm). This study underscores the importance of understanding DSD variability to enhance radar-based rainfall estimation and hydrological modelling. A comparison between 2019 and 2020 reveals that the reduction in pollution and changes in atmospheric conditions during the COVID-19 pandemic likely influenced raindrop formation processes. Specifically, 2020 shows a slightly higher concentration of larger droplets compared to 2019. Additionally, rainfall with lower intensity (5 mm/hr) in both years exhibits higher droplets, with the concentration decreasing as intensity increases. Reduced aerosol concentrations are likely responsible for fewer cloud condensation nuclei, resulting in larger cloud droplets and altered rainfall distribution. These changes in the microphysical properties of rain have significant implications for water resource management and flood prediction during extreme weather events. Overall, this study provides valuable insights into the environmental impact of human activities and highlights the interconnection between air quality and precipitation, contributing to improved weather forecasting accuracy and the development of more effective hydrological models.

Research highlights

Smaller raindrops (1 mm) consistently dominate the drop size distribution over Pune during all monsoon seasons (2018–2022).

June and September exhibit larger droplet sizes during high-intensity rainfall (50 mm/hr), while July–August show stable microphysical characteristics.

The monthly variation of b with higher values in September and moderate values in June points to a seasonal shift from convective to stratiform precipitation regimes.

The COVID-19 lockdown year (2020) shows a relative increase in larger raindrops at moderate to high intensities due to reduced aerosol loading.