Atmospheric Chemistry and Physics
Four different literature parameterizations for the formation and evolution of urban secondary organic aerosol (SOA) frequently used in 3-D models are evaluated using a 0-D box model representing the Los Angeles metropolitan region during the California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle- and gas-phase observations from the CalNex Pasadena ground site. That site provides a unique opportunity to study aerosol formation close to anthropogenic emission sources with limited recirculation. The model SOA that formed only from the oxidation of VOCs (V-SOA) is insufficient to explain the observed SOA concentrations, even when using SOA parameterizations with multi-generation oxidation that produce much higher yields than have been observed in chamber experiments, or when increasing yields to their upper limit estimates accounting for recently reported losses of vapors to chamber walls. The Community Multiscale Air Quality (WRF-CMAQ) model (version 5.0.1) provides excellent predictions of secondary inorganic particle species but underestimates the observed SOA mass by a factor of 25 when an older VOC-only parameterization is used, which is consistent with many previous model–measurement comparisons for pre-2007 anthropogenic SOA modules in urban areas.
Ahmadov, Ravan; Hayes, P.L.; Carlton, A.G.; Baker, K.R.; Washenfelder, R.A.; Alvarez, S.; Rappenglück, B.; Gilman, J.B.; Kuster, W.C.; Prévôt, A.S.H.; de Gouw, J.A.; Szidat, S.; Kleindienst, T.E.; Offenberg, J.H.; Ma, P.K.; and Jimenez, J.L., "Modeling the formation and aging of secondary organic aerosols in Los Angeles during CalNex 2010" (2015). Chemistry & Biochemistry Faculty Contributions. 38.