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https://doi.org/10.5194/egusphere-2025-5835
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2025-5835
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Preprints
12 Dec 2025
 | 12 Dec 2025
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Seasonal Variability and Cloud-Type Effects on Secondary Organic Aerosol Formation During Cloud Events at a Mountainous Site in Southeastern China

Yi Zhang, Weiqi Xu, Yan Li, Guohua Zhang, Dantong Liu, Ye Kuang, Yu Zhang, Wei Zhou, Xiaocong Peng, Bojiang Su, Weihong Huang, Zijun Zhang, Liu Yang, Yangzhou Wu, Siyuan Li, Shitong Zhao, Lanzhong Liu, Xiaole Pan, Zifa Wang, Xinhui Bi, Mikael Ehn, Douglas R. Worsnop, and Yele Sun

Abstract. Aerosol-cloud interactions exert substantial influences on atmospheric chemistry and regional climate, yet real-time characterization of chemical and microphysical evolution within cloud droplets remain limited. Here, two intensive campaigns were conducted at the high-altitude Shanghuang station in southeastern China during autumn 2023 and spring 2024, capturing distinct nocturnal orographic and long-persistence stratiform cloud events. Using a ground-based counterflow virtual impactor and an aerosol-cloud sampling inlet system along with integrated aerosol chemical speciation and cloud microphysical measurements, we resolved the composition of interstitial (INT), and residual (RES) particles during cloud events and ambient particles (AMB) under cloud-free conditions. Organic aerosols (OA) dominated particle mass across both seasons, while inorganic species (nitrate, sulfate, ammonium) exhibited high scavenging efficiencies (≥ 65–70 %) and strong enrichment in RES particles. Organic components showed seasonally contrasting partitioning patterns. Organics in INT particles exhibited a lower degree of oxidation during orographic clouds in 2023, whereas those in RES particles were more oxidized. In contrast, persistent clouds in 2024 displayed the opposite behaviour, reflecting shifts in aqueous-phase oxidation. Air-mass analysis further revealed pronounced source-dependent variability, with polluted westerly inflow leading to the highest particle loadings and most aged organic signatures. By linking chemistry with microphysics, we found that secondary organic aerosol formation preferentially occurs in smaller droplets, while OA from primary emissions is more efficiently incorporated into larger droplets through collision-coalescence. These results provide a quantitative, process-level understanding of seasonal and cloud-type controls on in-cloud chemical evolution, offering new constraints for representing aqueous-phase processing in atmospheric models.

How to cite. Zhang, Y., Xu, W., Li, Y., Zhang, G., Liu, D., Kuang, Y., Zhang, Y., Zhou, W., Peng, X., Su, B., Huang, W., Zhang, Z., Yang, L., Wu, Y., Li, S., Zhao, S., Liu, L., Pan, X., Wang, Z., Bi, X., Ehn, M., Worsnop, D. R., and Sun, Y.: Seasonal Variability and Cloud-Type Effects on Secondary Organic Aerosol Formation During Cloud Events at a Mountainous Site in Southeastern China, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-5835, 2025.
Received: 24 Nov 2025 – Discussion started: 12 Dec 2025

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Yi Zhang, Weiqi Xu, Yan Li, Guohua Zhang, Dantong Liu, Ye Kuang, Yu Zhang, Wei Zhou, Xiaocong Peng, Bojiang Su, Weihong Huang, Zijun Zhang, Liu Yang, Yangzhou Wu, Siyuan Li, Shitong Zhao, Lanzhong Liu, Xiaole Pan, Zifa Wang, Xinhui Bi, Mikael Ehn, Douglas R. Worsnop, and Yele Sun

Status: open (until 23 Jan 2026)

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Yi Zhang, Weiqi Xu, Yan Li, Guohua Zhang, Dantong Liu, Ye Kuang, Yu Zhang, Wei Zhou, Xiaocong Peng, Bojiang Su, Weihong Huang, Zijun Zhang, Liu Yang, Yangzhou Wu, Siyuan Li, Shitong Zhao, Lanzhong Liu, Xiaole Pan, Zifa Wang, Xinhui Bi, Mikael Ehn, Douglas R. Worsnop, and Yele Sun

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https://doi.org/10.5194/egusphere-2025-5835-supplement

Yi Zhang, Weiqi Xu, Yan Li, Guohua Zhang, Dantong Liu, Ye Kuang, Yu Zhang, Wei Zhou, Xiaocong Peng, Bojiang Su, Weihong Huang, Zijun Zhang, Liu Yang, Yangzhou Wu, Siyuan Li, Shitong Zhao, Lanzhong Liu, Xiaole Pan, Zifa Wang, Xinhui Bi, Mikael Ehn, Douglas R. Worsnop, and Yele Sun
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Short summary
This study explores how clouds influence the chemical composition of air particles through field research at a high-altitude station in southeastern China across different seasons. We found that different cloud types cause varying degrees of chemical changes in these particles. These findings enhance our understanding of the impact of clouds on air quality and contribute to improving climate models.
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