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Abstract
We investigate how a recently suggested pathway for production of secondary organic aerosol (SOA) affects the consistency of simulated organic aerosol (OA) mass in a global three-dimensional model of oxidant-aerosol chemistry (GEOS-Chem) versus surface measurements from the interagency monitoring of protected visual environments (IMPROVE) network. Simulations in which isoprene oxidation products contribute to SOA formation, with a yield of 2.0% by mass reduce a model bias versus measured OA surface mass concentrations. The resultant increase in simulated OA mass concentrations during summer of 0.6–1.0 μg m −3 in the southeastern United States reduces the regional RMSE to 0.88 μg m −3 from 1.26 μg m −3. Spring and fall biases are also reduced, with little change in winter when isoprene emissions are negligible.
Highlights
Aerosols influence climate through both direct and indirect means
We extend the work of Park et al (2003) by focusing on secondary organic aerosol (SOA) production during 2001 when biomass burning emissions are within 10% of the long-term mean
This is not meant to suggest that SOA formation from isoprene occurs at such high rates, but does show that this process can be readily accommodated within the current bias in modeled Organic aerosol (OA) concentrations
Summary
Analysis of springtime airborne measurements over the Northwest Pacific provide evidence that OA is the dominant component of aerosol mass in the free. Claeys et al (2004a, b) recently analyzed aerosols from the Amazonian forest and proposed that isoprene oxidation could provide an additional source of SOA via multiphase acid-catalyzed reactions with hydrogen peroxide. Edney et al (2005) found little evidence of isoprene-derived SOA formation in high atmospheric NOx conditions, but found a 2.8% yield in the presence of SO2. Field experiments by Matsunaga et al (2005) provide evidence that the isoprene oxidation products hydroxyacetone, methylglyoxal, and glycoaldehyde annually contribute 10–120 Tg of OA to the atmosphere. Henze and Seinfeld (2006) recently examined the global implications of SOA formation from isoprene oxidation products and found that the simulated SOA burden doubled. We compare surface measurements of OA with simulated OA over the continental United States to quantify how this process affects the comparison
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