| Abstract: |
Secondary organic aerosol (SOA), formed in the atmospheric oxidation of gas-phase organic compounds and subsequent gas-particle partitioning of lower-volatility reaction products, is known to be a major contributor to the total tropospheric particulate burden. Four studies [Heald et al., 2005, 2006; de Gouw et al., 2005; Volkamer et al., 2006], in which ambient measurements of OA in selected locations are compared with model predictions of OA, suggest that the amount of SOA in the atmosphere significantly exceeds that predicted by current models. Possible reasons for the discrepancy between SOA predictions and observations include: (1) SOA yields under atmospheric conditions for those parent hydrocarbons known to produce SOA exceed those measured in laboratory chambers; (2) Additional classes of SOA-forming hydrocarbons exist that have yet to be studied in the laboratory or included in atmospheric models; and (3) Uncertainties in current treatments of SOA formation in global models lead to biases that result in underpredictions; this includes, for example, emission inventories of major SOA precursors. |
