Journal Article

Turbulence‐Induced Non‐Monotonic Influence of Aerosols on Cloud Droplet Size Distribution

Zhu, Lei, Zhou, Zhuangzhuang, Lu, Chunsong, Lin, Pengcheng, Qin, Zhizhi, Chen, Yiqi, Yang, Jing, Chen, Jinghua, Chen, Jingyi, Chen, Qian

2025

Overview

Cloud droplet size distribution (DSD) is essential for quantifying the roles of clouds in earth system, including cloud albedo, precipitation formation, and cloud lifetime. The response of cloud droplet spectral relative dispersion (ε) to aerosol number concentration (Na) as well as the role of turbulence in this response are yet puzzling. This study uses large eddy simulation to examine the ε–Na relationship and derives an expression for ε from a minimal model to elucidate this relationship. Our findings indicate that as Na increases, ε initially decreases because aerosols weaken turbulence‐induced broadening more than condensational narrowing. However, as Na continues to rise, ε increases as aerosols weaken condensational narrowing more significantly than turbulence‐induced broadening. These findings improve the understanding of the aerosol effects on cloud DSD and address the challenge of quantifying aerosol indirect effects considering turbulence, potentially leading to new cloud microphysics parameterizations. Plain Language Summary The width of cloud droplet size distribution (DSD) significantly impacts cloud radiative properties and rain formations. However, its observed response to varying aerosol concentration is contrasting, and theoretical explanations are lacking. Using an advanced high‐resolution model, this study reveals that cloud DSD first narrows and then broadens as aerosol concentration increases. Furthermore, we propose a mathematical expression which explains the contrasting relationships by considering turbulence. These findings provide a comprehensive insight into the interplay between aerosol loading, cloud DSD, and turbulence within clouds. Key Points Cloud droplet size distribution first narrows and then broadens with increasing aerosol loading in large eddy simulations A minimal model is proposed to explain the non‐monotonic dependence of cloud droplet spectral relative dispersion on aerosol loading The results reconcile both non‐turbulent and turbulent scenarios regarding relationships between relative dispersion and aerosol loading

• Publisher: John Wiley & Sons, Inc
• Subject: Aerosol concentrations / Aerosol effects / aerosol indirect effect / Aerosols / Albedo / Cloud albedo / Cloud droplet size / Cloud droplet size distribution / Cloud droplets / Cloud formation / Cloud microphysics / Clouds / Droplets / Large eddy simulation / Large eddy simulations / Microphysics / Precipitation formation / relative dispersion / Size distribution / Turbulence