Abstract This study reports on new particle formation (NPF) and characteristic features observed from a rural site falling in the rainshadow of the Western Ghats in peninsular India. A total of 35 NPF events observed during August 2018 - January 2019 are classified and analyzed here. The apparent formation rates ranged from 0.2 to 10.0 cm–3 s–1, while the growth rates of nucleation mode particles ranged from 1.2 to 13.8 nm h–1. The frequency of occurrence was least during August (core monsoon) and highest during post-monsoon. The local winds were calm and southeasterly to easterly (from the urban centre) supplying the essential precursor gases during October and November, leading to a frequent occurrence of nucleation events. Observations suggest that an increased condensation sink could limit the NPF while promoting Aitken mode growth. The newly formed particles accounted for about 10–80% of the total aerosol concentration. These newly formed particles were able to act as cloud condensation nuclei after growing to approximately 50 nm with an average activation fraction of 0.4.

中文翻译：

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从印度西高止山脉的雨影区观察到的新粒子形成

摘要 本研究报告了从落入印度半岛西高止山脉雨影中的农村遗址观察到的新粒子形成 (NPF) 和特征特征。此处对 2018 年 8 月至 2019 年 1 月期间观察到的总共 35 个 NPF 事件进行了分类和分析。表观形成速率范围为 0.2 至 10.0 cm-3 s-1，而成核模式粒子的生长速率范围为 1.2 至 13.8 nm h-1。发生频率在 8 月（核心季风）最少，在后季风发生频率最高。10 月和 11 月期间，当地风平静，东南风到东风（从市中心）提供必要的前体气体，导致成核事件频繁发生。观察表明，增加的冷凝汇可能会限制 NPF，同时促进 Aitken 模式的增长。新形成的颗粒约占总气溶胶浓度的 10-80%。这些新形成的粒子在生长到大约 50 nm 后能够充当云凝结核，平均激活分数为 0.4。