AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Global Modeling of Secondary Organic Aerosol Production from Reaction of NO3 Radical with Speciated Monoterpenes
MAKOTO KELP, Havala Pye, Emily Fischer, Jared Brewer, Juliane L. Fry, Reed College
Abstract Number: 646 Working Group: Aerosol Chemistry
Abstract Historically, global modeling of secondary organic aerosol (SOA) formation from monoterpenes has been based on a simple lumped mechanism, which parameterizes all monoterpene + NO3 reactions as having the aerosol yield of beta-pinene + NO3. The resulting global spatial patterns and annual budgets of organic aerosol often do not match observations, and are inconsistent with recent chamber studies revealing alpha-pinene reaction with NO3 radical oxidant to have a much lower SOA yield than compared to the other bicyclic monoterpenes. To assess how a more realistic, lower alpha-pinene + NO3 SOA-producing pathway affects global organic aerosol concentrations, the global 3-D chemical transport model GEOS-Chem was updated with a new volatility basis set (VBS) based aerosol parameterization where alpha-pinene was unlumped from the lumped parameterized terpenes tracer and speciated with unique chemistry. As a result of this new parameterization, there were predicted model differences of up to 3.5 ug/m3 less SOA in the summer months in high organic aerosol producing source regions. Integrated over the globe, the reduction led to an annual decrease of 2 Tg yr-1 organic aerosol between the control and novel VBS mechanism, a 10% change from previous model terpene organic aerosol budgets. This work demonstrates that lumped terpene mechanisms may cause substantial errors in predicting SOA spatial patterns, with consequences for global budgets of highly climate relevant aerosol mass loading.