The regional atmospheric chemistry mechanism, version 2

The Regional Atmospheric Chemistry Mechanism (RACM) is a gas-phase chemical mechanism that is widely used for the modeling of regional atmospheric chemistry. Much new data has been published since the original RACM was completed (Stockwell et al., 1997). The RACM mechanism was updated to create the Regional Atmospheric Chemistry Mechanism, version 2 (RACM2). Like the RACM1 mechanism, the RACM2 mechanism is designed to simulate remote to polluted conditions from the Earth's surface through the upper troposphere. The RACM2 mechanism includes updated reaction schemes, rate constants and product yields. It has been tested against environmental chamber data and compared with previous RACM scenario simulations. The aromatic chemistry was expanded to include a greater number of species with highly revised reaction schemes. The reaction mechanism for isoprene was expanded to include a more explicit treatment of methyl vinyl ketone. Alcohols were speciated to more accurately reflect peroxy–peroxy reactions in the remote atmosphere. Acetone was speciated due to its importance in the upper troposphere.

► The RACM2 mechanism includes updated reactions, rate constants and product yields.
► It has been tested against environmental chamber data.
► The aromatic chemistry was expanded to include a greater number of species.
► The reaction mechanism for isoprene was expanded.