A new sensitivity analysis of algorithms for estimating organic aerosol (OA) is presented, conducted using the CAMx air quality model with both a traditional two-product scheme (SOAP) and the latest Volatility Basis Set (VBS) algorithm. Sensitivity simulations include default versions of both SOAP and VBS schemes, along with new parameterizations for the VBS scheme to calculate emissions and volatility distributions of semi-volatile and intermediate-volatility organic compounds. The focus of the simulations is the summer season (from May to July 2013) to quantify the model’s sensitivity during a period of more intense photochemical activity compared to winter.

In addition to the model sensitivity analysis, the obtained results were compared with OA measurements from aerosol mass spectrometers at two monitoring sites. Unlike previously published winter cases, the comparison with experimental data showed limited sensitivity to the increase in total OA, restricted to a few tenths of µg m-3, for both primary and secondary components. The lower sensitivity compared to winter conditions is primarily linked to the reduced influence of the examined emission sectors on summer aerosol. Furthermore, the reduced sensitivity to new parameterizations could be associated with the higher partitioning of OA into the gas phase during the summer period, thereby reducing the organic fraction in the aerosol phase.