The sensitivity of ozone and hydroxyl to increased speciation of ketones in the new Regional Atmospheric Chemistry Mechanism, Version 2

The new Regional Atmospheric Chemistry Mechanism, Version 2 (RACM2) contains the speciated ketones acetone, methyl ethyl ketone, and methyl vinyl ketone, as well as higher ketones aggregated as KET, while the previous version of the Regional Atmospheric Chemistry Mechanism (RACM) (Stockwell et al., 1997) aggregates all ketones into a single species (KET). An atmospheric chemistry box-model (SBOX: Seefeld, 1997) is used to estimate the impact of the increased speciation of ketones on ozone and hydroxyl concentrations for the new RACM2 as compared to the older RACM scheme using aloft conditions in the free troposphere. As RACM treats KET as a mixture of acetone and methyl ethyl ketone, RACM2's treatment of acetone and methyl ethyl ketone explicitly is compared to RACM's KET. The effect of the increased speciation of ketones is also investigated as a function of altitude.