10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
A Simplified Parameterization of Isoprene Epoxydiols Derived Secondary Organic Aerosol (IEPOX-SOA) for Global and Climate Models
DUSEONG JO, Alma Hodzic, Louisa Emmons, Eloise Marais, Zhe Peng, Weiwei Hu, Pedro Campuzano-Jost, Jose-Luis Jimenez, University of Colorado Boulder
Abstract Number: 265 Working Group: Aerosol Chemistry
Abstract Isoprene is the most abundant non-methane volatile organic compound in the atmosphere and substantially contributes to secondary organic aerosol (SOA) concentrations globally. Isoprene epoxydiols derived SOA (IEPOX-SOA) is thought to contribute the dominant fraction of total isoprene SOA. IEPOX-SOA depends on aerosol pH and other properties, and cannot be calculated accurately with lumping SOA schemes such as two-product and volatility basis set approaches. Recent modeling studies have found generally good agreement between simulated and observed IEPOX-SOA after including detailed isoprene chemistry. However, these models require high computational cost including the calculations of chemistry, deposition, and transport processes of intermediates (e.g. isoprene peroxy radicals, ISOPOOH, IEPOX, etc.). This makes it difficult to include into climate models for long-term studies. For similar reasons, the latest version of the GEOS-Chem model includes a fixed 3% yield of SOA from isoprene for most model applications, in order to avoid the extra computational cost of the full mechanism. Here we present a simplified parameterization for IEPOX-SOA simulation, based on an approximate analytical solution of the relevant portion of the isoprene chemical mechanism. The IEPOX-SOA yield and formation timescale can be directly calculated using the current model fields of oxidant concentrations, NO, aerosol pH and other key properties, and dry deposition rates. Therefore, the parameterization does not require the simulation of the intermediates with maintaining chemical fidelity for simulating IEPOX-SOA. The simulated IEPOX-SOA with the parameterization shows R2 of 0.96 in comparison to that with the full chemistry in terms of temporal (timeseries in source region) and spatial (global map) variations. Detailed methodology and evaluation results of the parameterization will be discussed.