Preprints
https://doi.org/10.5194/egusphere-2024-4037
https://doi.org/10.5194/egusphere-2024-4037
30 Jan 2025
 | 30 Jan 2025
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Aerosol impacts on regional climate: chaotic or physical effect?

Jiawang Feng, Chun Zhao, Jun Gu, Gudongze Li, Mingyue Xu, Shengfu Lin, and Jie Feng

Abstract. Aerosols have significant impacts on regional climate, which has been widely investigated with numerical experiments. However, uncertainties of simulated aerosol impact due to long-standing chaotic effect remain unclear. Here we propose a diagnostic method based on large ensemble simulations and random sampling algorithm to unveil the chaos-induced uncertainties in simulated aerosol climatic impacts that is overlooked in previous studies. Taking dust impacts on Indian summer monsoon system as a demonstration, our findings reveal that, while dust generally enhances the large-scale summer monsoon circulation consistently among ensemble members, its impacts on regional systems, such as monsoon depressions, exhibit significant chaotic effect: the simulated aerosol impacts on precipitation from individual ensemble member differ substantially, even inversely. Through quantitative analysis, we demonstrate that the magnitude of these chaotic effects diminishes following a N relationship with ensemble size N. Furthermore, our results indicate that statistical significance testing alone may be insufficient for robust attribution of dust impacts, as even small ensembles can yield statistically significant yet contradictory results. This study emphasizes the necessity of employing adequate ensemble sizes to capture reliable physical impacts of aerosol on regional climate.

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Jiawang Feng, Chun Zhao, Jun Gu, Gudongze Li, Mingyue Xu, Shengfu Lin, and Jie Feng

Status: open (until 13 Mar 2025)

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Jiawang Feng, Chun Zhao, Jun Gu, Gudongze Li, Mingyue Xu, Shengfu Lin, and Jie Feng
Jiawang Feng, Chun Zhao, Jun Gu, Gudongze Li, Mingyue Xu, Shengfu Lin, and Jie Feng

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Short summary
Climate models help study aerosol impacts on regional climate. However, the atmosphere's chaotic nature makes it hard to separate true aerosol impacts from chaotic effects. Our ensemble experiments show that while large-scale aerosol effects are consistent, regional aerosol impacts vary significantly among experiments. We give a formula showing the relationship between chaotic effects and ensemble sizes, emphasizing the necessity of adequate ensemble members to capture reliable aerosol impacts.
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