Rapid Changes in the Particle Mixing State through Cloud Processing

LAURA FIERCE, Payton Beeler, Alla Zelenyuk, ManishKumar Shrivastava, Nahin Ferdousi, Pacific Northwest National Laboratory

     Abstract Number: 520
     Working Group: Aerosols, Clouds and Climate

Abstract
Aerosol transformations during cloud processing play a critical role in the aerosol lifecycle, but these aerosol-cloud processes remain poorly understood. Aerosol particles are critical for cloud droplet formation, and their ability to form cloud droplets depends small-scale variability in aerosol properties that are not easily modeled or measured. After forming cloud droplets, particle characteristics are further modified through chemistry. Single-particle measurements from DOE’s Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) campaign revealed large differences between cloud droplet residuals and aerosol particles at cloud base. These differences may result from preferential activation of one particle type over another, in-cloud chemistry, or a combination of the two. To disentangle the processes driving the evolution of the mixing state, we introduce the PArtiCle-based Aerosol-Cloud-chEmistry (PALACE) model, which tracks the evolution of individual particles as they evolve through cloud processing. Modeled particle populations were initialized using below-cloud aerosol observations from HI-SCALE, and model predictions were evaluated against observations of cloud droplet residuals. The observed changes in the particle mixing state are captured only when both preferential scavenging and aqueous chemistry are included in the model. This study represents an important step toward integrating particle-resolved modeling with single-particle measurements, while also advancing our process-level understanding of the aerosol lifecycle.