Raindrop size distribution (RSD) is crucial for accurate quantitative precipitation estimation and forecasting and is fundamental to precipitation microphysics. This study examines the microphysical characteristics of RSD at Rourkela, Odisha, under polluted and non-polluted conditions. This investigation utilized pre-monsoon in-situ (disdrometer) and reanalysis (ERA5) data for 2018–2021, to identify the pollution impact on precipitation over Rourkela. The polluted rainfall day has been determined based on the air quality index (AQI) value provided by the Central Pollution Control Board (CPCB), Government of India, over the Rourkela region. Classifying the rainfall in polluted and non-polluted days into stratiform and convective types showed that convective rainfall had a higher raindrop concentration and higher mean diameter (Dm) in both polluted and non-polluted days. Convective rainfall has a lower normalized intercept parameter (log10Nw) in polluted rainfall days. The RSD empirical relations (Z-R, μ – λ, Dm-R, Nw-R) also showed a noteworthy difference between the polluted and non-polluted rainfall days. The results disclosed that non-polluted rainfall has higher concentration of small-diameter raindrops, whereas polluted day rain has higher concentrations of midsize and large-diameter raindrops.

中文翻译：

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印度鲁尔克拉季风前污染雨天和非污染雨天雨滴大小分布对比


雨滴尺寸分布 (RSD) 对于准确定量降水估算和预报至关重要，也是降水微物理的基础。本研究考察了奥里萨邦 Rourkela 在污染和非污染条件下 RSD 的微物理特征。这项调查利用了 2018 年至 2021 年季风前的现场（测速仪）和再分析 (ERA5) 数据，以确定污染对 Rourkela 降水的影响。污染降雨日是根据印度政府中央污染控制委员会（CPCB）提供的鲁尔克拉地区空气质量指数（AQI）值确定的。将污染天和非污染天的降雨分为层状和对流类型表明，污染天和非污染天的对流降雨具有较高的雨滴浓度和较高的平均直径（Dm）。在污染降雨天，对流降雨具有较低的归一化截距参数（log10Nw）。 RSD 经验关系（ZR、μ – λ、Dm-R、Nw-R）也显示污染和非污染降雨天数之间存在显着差异。结果表明，未受污染的降雨中小直径雨滴的浓度较高，而受污染的日间降雨中中大直径雨滴的浓度较高。