Cloud Droplet Nucleation Simulation and Parameterization

作者：Jiming Sun, Jun Zhang, Wei Deng, Wenhao Hu, Yongqing Wang · 发表于：Journal of the Atmospheric Sciences · 年份：2022 · DOI：10.1175/jas-d-22-0010.1 · 被引用次数：5 · 研究领域：Atmospheric aerosols and clouds、Atmospheric chemistry and aerosols、Aeolian processes and effects

Abstract Cloud droplet nucleation is classically defined as a droplet growing to a size such that its ambient supersaturation exceeds its surface equilibrium water vapor pressure. Unactivated particles are always in equilibrium with the ambient vapor pressure. Further studies showed that such an equilibrium assumption leads to many more cloud droplets being nucleated due to neglecting kinetic growth limitations, including the inertial mechanism, evaporation mechanism, and deactivation mechanism. Moreover, the inertial mechanism results in great discrepancy between the actual size and the critical size of nucleation for large aerosol particles. These issues complicate cloud droplet nucleation parameterization for applications in cloud modeling. To establish a physically based nucleation scheme, we established a highly size-resolved Lagrangian parcel model. Vapor diffusion and heat conduction were calculated according to Maxwell theory, and the surface vapor density and temperature were explicitly simulated. The surface temperature variation of a droplet with its size was considered. The surface supersaturation of a droplet, taking into account the surface temperature variation, is different from its equilibrium supersaturation at its large sizes. The nucleation simulation showed that the inertial and deactivation mechanisms can impact droplet nucleation. Moreover, very large nuclei can trigger rain embryo formation in a short time period. Even though there are kinetic limitati...