Figure 4.

OOA concentrations (μg m⁻³) at California sites as a function of the measured O_x (O₃ + NO₂) concentration. A background concentration, O_x (BG), of 13.5 ppbv is assumed, consistent with Hayes et al. (2015). The boxes behind each trend indicate the 25th and 75th percentiles of the data. The whiskers extend to the 10th and 90th percentiles. The solid horizontal lines in each box identify the median, and the solid curves indicate the means of each model run. Model values are projected to PM₁ to correspond roughly to the size cutoff of the AMS.