Chemical mechanisms in two photochemical modelling systems: A comparison procedure

The main purpose of this study is the evaluation of different chemical mechanisms included in two Eulerian photochemical models, MARS and CAMx, comparing simulation results. Both mechanisms (KOREM and EMEP) included in MARS were applied, whereas concerning CAMx the tested mechanisms were the default Carbon Bond IV and the revised radical termination reactions for the same mechanism. These two models were applied to a Portuguese coastal region, Aveiro, where a field campaign was carried out during a summer period, from 25(th) June to 2(nd) July 2001. The understanding of the influence of mesoscale meteorological phenomena on the ozone production over the region of interest was the major objective of this field campaign, which was designed considering photochemical modelling evaluation. Therefore, a 48 hours simulation was performed using a 200 x 140 km(2) domain. Meteorological inputs to both photochemical models were obtained by the application of the mesoscale meteorological model MM5 using its nesting capabilities. Meteorological and ozone concentration simulation results were evaluated using the data collected during the field campaign. Preliminary results concerning the different chemical schemes applied, KOREM, EMEP and CB-IV, present a good skill for ozone peak simulations. All mechanisms may be applied for population alert situations. Although, it is important to notice that KOREM scheme offers an interesting and simple operative solution for the study region.