AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Evaluating the Impacts of In-Cloud Chemistry on Resuspended Aerosol Particles after Cloud Evaporation using a Particle Resolved Model
YU YAO, Nicole Riemer, Matt Dawson, University of Illinois at Urbana-Champaign
Abstract Number: 295 Working Group: Aerosols, Clouds and Climate
Abstract Aerosol particle size distributions undergo physical and chemical changes during cloud processing. After cloud evaporation, the released particles can have different activation potentials than the particles before cloud processing because of changes in size and chemical composition. Current models use simplified assumptions about these mass and size changes due to cloud processing. For example, the aerosol module coupled to WRF-Chem assumes the cloud-borne aerosol mass is proportional to cloud droplet mass, and in the Community Multiscale Air Quality Modeling System (CMAQ), it is assumed that the mass formed by aqueous phase chemistry is added to the accumulation mode aerosol. In real environments, particles with different composition and size experience different net effects from aqueous chemical processing, so the impact of in-cloud chemistry on the resuspended aerosol size distribution can be more complicated.
In this study, we focus on the resuspension of aerosol populations, and the changes of aerosol microphysical properties after cloud evaporation. We simulated several urban plume scenarios that produced populations with a wide variety of aerosol mixing states using the particle-resolved model PartMC-MOSAIC. These simulated aerosol populations were then used as the input for cloud parcel simulations, including aqueous chemistry, at various cooling rates. The aqueous chemistry mechanism coupled to the model is based on a reduced version of CAPRAM 2.4 developed by Ervens et al. in 2003, which includes 121 aerosol species and 178 reactions. The particle-resolved approach is well-suited for this problem because it can track the evolution of compositions and sizes of individual aerosol particles without averaging their composition within size bins or modes. We will quantify the species mass and particle size differences of the aerosol population before and after cloud processing, and relative changes to critical supersaturations will be used to evaluate the microphysical changes.