A supplement for the RADM2 chemical mechanism: The photooxidation of isoprene

We have developed an extension of the RADM2 chemical mechanism by a comprehensive isoprene chemistry. This extended mechanism (RADM-E) leads to the same results as RADM2 for vanishing concentrations of isoprene. Since RADM-E includes 39 new species and 153 additional reactions, it is not suitable for use in three-dimensional models. Therefore, a condensed mechanism (RADM-C) was developed with only six new species and 16 additional reactions. In three scenarios, covering clean to polluted situations with high impact of isoprene, the chemical mechanisms RADM2, RADM-E, and RADM-C are compared by means of a simple two-box model. Differences of concentrations between RADM2 and the other mechanisms can exceed 10% for O3 and a factor of 2 for HOx, peroxides, NOx, PAN, and HNO3. Carbonyl compounds show even higher differences. RADM-C gives approximately the same results as RADM-E.