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Trends and Variability in Concentrations and Source Contributions of 2002 – 2019 Ozone and Particulate Matter over the Northern Hemisphere
Citation:
Hogrefe, C., R. Mathur, S. Napelenok, B. Henderson, G. Sarwar, G. Pouliot, J. Willison, R. Gilliam, Keith Appel, Bill Hutzell, D. Kang, B. Murphy, H. Pye, AND K. Foley. Trends and Variability in Concentrations and Source Contributions of 2002 – 2019 Ozone and Particulate Matter over the Northern Hemisphere. ITM 2023 International Technical Meeting On Air Pollution Modeling And Its Application, Chapel Hill, NC, May 22 - 26, 2023.
Impact/Purpose:
This abstract and eventual presentation provide an overview of the 2002 – 2017 hemispheric CMAQ simulations performed for the EQUATES project. These simulations serve a dual purpose: they provide a characterization of large-scale background concentrations and their trends and variability for the 2002 – 2017 12 km CMAQ simulations performed over the conterminous U.S., and they also serve as a computationally efficient testbed for exploring model sensitivities and effect of model updates over extended spatial and temporal scales. Performing a detailed evaluation of these simulations can be used to guide future model development.
Description:
Large-scale chemistry transport models, such as the hemispheric configuration of the Community Multiscale Air Quality (CMAQ) model, can be used to study drivers of trends and variability in tropospheric ozone, other trace gases, and aerosols that affect estimated background conditions for regional model applications. In this study, we present results from 2002 – 2019 CMAQ simulations performed over the Northern Hemisphere for EPA’s Air QUAlity TimE Series Project (EQUATES) project. The EQUATES project is aimed at studying historic air quality at hemispheric-to-regional scales with a consistent set of modeling approaches, with a particular focus on the United States. The hemispheric CMAQ fields are evaluated against surface observations, satellite retrievals, and ozonesonde observations for different regions. Initial results indicate a persistent overestimation of summertime surface ozone and a tendency to underestimate springtime ozone at both the surface and aloft. Regional variations in modeled ozone trends are found to be in good agreement with observations across a range of percentiles. Model sensitivity simulations were performed to estimate the impacts of different representations of biogenic volatile organic compound emissions, soil nitrogen oxide emissions, and WRF (Weather Research and Forecasting model) cumulus parameterization on model estimates. Results of the WRF cumulus parameterization sensitivity indicate a pronounced impact on precipitation and aerosols, with competing effects for ozone. The CMAQ Integrated Source Apportionment Method (ISAM) tool is used to estimate the contributions of emissions from anthropogenic and natural (fires, biogenic volatile organic compounds, soil nitrogen oxide, and wind-blown dust) sources from different regions to simulated concentrations for selected years throughout the 18-year period. These source contributions are then analyzed to determine their spatial and temporal fluctuations and their influences on seasonal and interannual variability and long-term trends of estimated background concentrations over the United States. Disclaimer: The views expressed in this abstract are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency (EPA).