On Friday, April 8 at 2:00 PICS will host a colloquium featuring Dr. Rahul Zaveri, Scientist, Atmospheric Sciences & Global Division, Pacific Northwest National Laboratory.
Title: The Dynamics of Gas-Particle Partitioning: Insights from Laboratory, Field, and Modeling studies
Ultrafine aerosols can significantly influence Earth’s climate if they are able to grow to sizes large enough to interact with the incoming solar radiation and nucleate cloud droplets. In clear air, aerosol growth occurs via gas-to-particle conversion of condensable trace gases, including sulfuric acid, nitric acid, hydrochloric acid, ammonia, and myriad oxidation products of many different volatile organic compounds. Nearly all aerosol models developed to date to simulate the aerosol growth assume instantaneous equilibrium between semivolatile gases and submicron-sized particles. This assumption effectively favors the growth of the largest pre-existing particles in accordance with Raoult’s law. In this talk, I will use a combination of laboratory, field, and modeling studies to show that the equilibrium assumption may not always hold, especially when aerosol growth occurs from condensation of supersaturated vapors and/or when the pre-existing aerosols are in a solid or semisolid phase state. In such cases, gas-particle partitioning must be treated as a dynamic process and size-resolved bulk diffusion limitation must be considered inside semisolid particles. I will outline a computationally efficient dynamic gas-particle partitioning treatment in the MOSAIC aerosol model to address this issue and discuss implications on the growth of ultrafine aerosols from semivolatile vapors.
Bio: Rahul Zaveri has a wide range of research experience in investigating the fate of anthropogenic and biogenic trace gas and aerosol emissions and their effects on air quality and climate change. His expertise is in modeling the complex physical and chemical processes occurring in the gas-, aerosol-, and cloud-phases and their climate-related properties. He is the scientific lead for the gas-phase photochemical mechanism CBM-Z and the comprehensive aerosol model MOSAIC, which have been implemented in the fully-coupled meteorology-chemistry model WRF-Chem. Dr. Zaveri has also participated in and led field campaigns to study the formation and evolution of oxidants and aerosols and their climate-related properties downwind of large urban areas.