Abstract
Abstract. We present results from and evaluate the performance of a 12-month, 12 km horizontal resolution year 2005 air pollution simulation for the contiguous United States using the WRF-Chem (Weather Research and Forecasting with Chemistry) meteorology and chemical transport model (CTM). We employ the 2005 US National Emissions Inventory, the Regional Atmospheric Chemistry Mechanism (RACM), and the Modal Aerosol Dynamics Model for Europe (MADE) with a volatility basis set (VBS) secondary aerosol module. Overall, model performance is comparable to contemporary modeling efforts used for regulatory and health-effects analysis, with an annual average daytime ozone (O3) mean fractional bias (MFB) of 12% and an annual average fine particulate matter (PM2.5) MFB of −1%. WRF-Chem, as configured here, tends to overpredict total PM2.5 at some high concentration locations and generally overpredicts average 24 h O3 concentrations. Performance is better at predicting daytime-average and daily peak O3 concentrations, which are more relevant for regulatory and health effects analyses relative to annual average values. Predictive performance for PM2.5 subspecies is mixed: the model overpredicts particulate sulfate (MFB = 36%), underpredicts particulate nitrate (MFB = −110%) and organic carbon (MFB = −29%), and relatively accurately predicts particulate ammonium (MFB = 3%) and elemental carbon (MFB = 3%), so that the accuracy in total PM2.5 predictions is to some extent a function of offsetting over- and underpredictions of PM2.5 subspecies. Model predictive performance for PM2.5 and its subspecies is in general worse in winter and in the western US than in other seasons and regions, suggesting spatial and temporal opportunities for future WRF-Chem model development and evaluation.
Highlights
Epidemiological studies have established the importance of health effects from acute and chronic exposure to fine particulate matter (PM2.5) and ground-level ozone (O3) (Jerrett et al, 2009; Krewski et al, 2009; Pope III and Dockery, 2006)
We present here WRF-Chem results from a full year, 12 km resolution simulation for the contiguous US, evaluate the performance of the model compared to ambient measurements, and compare WRF-Chem performance to published goals and criteria (Boylan and Russell, 2006) and to recent Community Multiscale Air Quality (CMAQ) results for a similar simulation (Appel et al, 2012)
The volatility basis set (VBS) approach differs from other secondary organic aerosol (SOA) parameterizations in that it assumes that primary organic aerosol (POA) is semi-volatile
Summary
Epidemiological studies have established the importance of health effects from acute and chronic exposure to fine particulate matter (PM2.5) and ground-level ozone (O3) (Jerrett et al, 2009; Krewski et al, 2009; Pope III and Dockery, 2006). The accuracy of health-impact predictions for future air pollutant emissions (e.g., Tessum et al, 2012, 2014) depends in part on the performance of air quality models over long timescales and in all seasons. Accurate health-impact predictions often depend on model simulations that cover large geographic areas such as the contiguous US, so as to capture the full impacts of the long-range transport of pollutants (Levy et al, 2003). Whereas chemical transport model (CTM) simulations for a full year for the contiguous US often use 36 km horizontal grids (e.g., Tesche et al, 2006; Yahya et al, 2014), increasing horizontal grid resolution to 12 km can result in the more accurate prediction of pollutant concentrations (Fountoukis et al, 2013) and population exposure.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
