Comparison of the MC2/CALGRID and SAIMM/UAM-V photochemical modelling systems in the Lower Fraser Valley, British Columbia

An ozone episode in the Lower Fraser Valley, British Columbia is simulated using the same emission inventory in two modelling systems: MC2/CALGRID and SAIMM/UAM-V. Spatial and temporal variations of modelled concentrations of O3, NO, NO2, and CO are compared with observations. Concentrations of PAN, HONO, HNO3, HCHO, higher aldehydes, and H2O2 from each model are compared. Several statistical criteria are used in the comparisons. In general, the agreement between the models is better than the agreement with observations, and both models tend to underpredict peak ozone and overpredict nighttime minimum ozone. The major features of the response of the models to a 30% reduction in total NOx or VOC emissions in the Lower Fraser Valley are also comparable. The elements of the photochemical models that could contribute to the behavior of the models are discussed.