An evaluation of the predictive performance of the photochemical grid models UAM-V and CAMx for the northeast corridor
- NOAA, Silver Spring, MD (United States). Air Resources Lab.
A significant feature of the Northeastern US is that ozone concentrations exceed the federal standard of 120 ppb several times every year. This results in an elevated background level for ozone concentrations even at sites located far from major nonattainment areas. New emission control strategies depend strongly on the application of well evaluated photochemical models on a regional and urban scale. Therefore, a need exists to evaluate photochemical grid models regarding their reliability in simulating ozone and precursor concentrations. This study compares the performance of the two photochemical grid models UAM-V and CAMx. To assure a fair comparison, the models were run over the same modeling domain with the same grid size, meteorological input, initial and boundary conditions. Identical inputs of source emissions were applied to compare peak and average ozone concentrations in space and time at four urban sites along the Northeast Corridor. Results indicate in general a good agreement with observed data. In this study CAMx performs slightly better in simulating hourly ozone concentrations than the UAM-V with R2 = 0.89 against R2 = 0.85. Both models tend to over predict hourly ozone concentrations when less than 40 ppb and under predict when above 80 ppb. An analysis of the performance of CAMx and UAM-V simulating ozone concentrations during daylight hours implicates that in general both models follow changes from increasing to decreasing ozone levels too slowly and vice versa. The main reason for this feature might be caused by a concept implemented in the models` source codes which improperly calculates vertical diffusion of chemically active tracers like NO and NO{sub 2}. Furthermore the authors examined how close to observed data both models calculate the Isoprene/NO{sub x} ratio for urban sites. Results of this analysis indicates how well a model will respond to NO{sub x} and VOC control strategies in terms of ozone abatement strategies
- OSTI ID:
- 362040
- Report Number(s):
- CONF-980632--
- Country of Publication:
- United States
- Language:
- English
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