Citation:

Hogrefe, C., K. Foley, Keith Appel, S. Roselle, D. Schwede, J. Bash, AND R. Mathur. Air Pollution Modeling and its Application XXVII: Evaluating Long-Term Ozone and PM2.5 Simulations Over the United States. Air Pollution Modeling and its Application XXVII. Springer Berlin - Heidelberg, , Germany, , 345-351, (2021). https://doi.org/10.1007/978-3-662-63760-9_50

Impact/Purpose:

By comparing observed and CMAQ-simulated long-term ozone variations and trends, the work in this study addresses the question of how well CMAQ performs when applied to simulate the effects of changing emissions and meteorological variability on ambient ozone. The study examines two sets of simulations that differ in two of the key input fields, i.e. anthropogenic emissions and boundary conditions. Results of this analysis can inform model development efforts by focusing such efforts on processes and input fields most directly connected to the model’s ability in reproducing observed variability and trends.

Description:

In this study, we analyzed ozone and total and speciated PM2.5 fields from two sets of WRF/CMAQ simulations over the continental US. Results show that differences in trends of ozone boundary conditions affect trends in modeled surface ozone concentrations within the domain, especially during fall and winter. The analysis of total and speciated PM2.5 showed best model performance for SO42− and revealed that modeled seasonal cycles of organic carbon in urban areas differed from observations for both simulations. It is likely that uncertainties in primary PM2.5 emissions along with assumptions about the volatility of primary organic aerosols and the formation of secondary organic aerosols made in these simulations caused these differences and that recent updates made to the treatment of organic aerosol processes in CMAQ would lead to improved model performance.

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