The present study aims to quantify the raindrop size distributions (RSDs) of Indian summer monsoon (ISM) rainfall over a tropical eastern Indian station, Rourkela using five years (2018–2021) of Thies disdrometer measurements. The RSD measurements of ISM rainfall at Rourkela are segregated into active and break spells using the standardized rainfall anomalies over the study area. The RSDs characteristics of active and break spells are analyzed and their empirical relations, which are appropriate for precipitation estimation algorithms, are also reported. A significant annual and monthly variations in RSDs is noticed between the active and break spells of the ISM rainfall over the study region. The probability distribution function (PDF) RSDs parameters (rainfall rate, liquid water content, mass-weighted mean diameter, and normalized intercept parameter) demonstrated clear distinctions between active and break spells. The active spells showed higher rainfall amounts, large mass-weighted mean diameter, and smaller normalized intercept parameters over the break spells. A further segregation of active and break spells into stratiform and convective types revealed more large size drops in convective (stratiform) precipitations of active (break) spells. Occurrence of higher rainfall amounts and large size raindrops in the active spells over the break spells can be attributed to the presence of abundant moisture and convective activity in active spells. Furthermore, the radar reflectivity-rainfall rate (), shape and slope (), and mass-weighted mean diameter-rainfall rate (-) relations established for the active and break spells could aid in improving the precipitation estimations of over the study region.

中文翻译：

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印度东部夏季季风降雨的雨滴大小分布


本研究旨在利用泰斯测距仪五年（2018-2021）的测量结果，量化印度东部热带站 Rourkela 上空的印度夏季季风 (ISM) 降雨量的雨滴大小分布 (RSD)。 Rourkela ISM 降雨的 RSD 测量值使用研究区域的标准化降雨异常分为活跃时段和中断时段。分析了活动期和间歇期的 RSD 特征，并报告了它们适用于降水估计算法的经验关系。在研究区域 ISM 降雨的活跃期和间歇期之间，RSD 存在显着的年度和月度变化。概率分布函数 (PDF) RSD 参数（降雨率、液态水含量、质量加权平均直径和归一化截距参数）显示出活跃期和中断期之间的明显区别。与中断时段相比，活跃时段显示出较高的降雨量、较大的质量加权平均直径和较小的归一化截距参数。将活跃和中断事件进一步分为层状和对流类型，发现活跃（中断）事件的对流（层状）降水有更大尺寸的下降。活动期间出现较高的降雨量和较大尺寸的雨滴可归因于活动期间存在丰富的水分和对流活动。此外，为活跃期和间歇期建立的雷达反射率-降雨率 ()、形状和坡度 () 以及质量加权平均直径-降雨率 (-) 关系有助于改进研究区域的降水估计。