||Dynamic Evaluation of 2006 ©¢â‚¬â€œ 2010 Ozone Trends in AQMEII-2 North American Domain Simulations.
T. E., Stoeckenius ;
C., Hogrefe ;
||ENVIRON International Corp., Novato, CA.; Coordinating Research Council, Inc., Alpharetta, GA.; Environmental Protection Agency, Washington, DC.
Air quality ;
Computer models ;
Photochemical grid model ;
Particulate matter ;
Graphical evaluation ;
Ensemble predictions ;
NOx emission standards ;
Meteorological conditions ;
Ozone concentration ;
Comprehensive Air Quality Model with Extensions(CAMx) ;
Air Quality Model Evaluation International Initiative(AQMEII) ;
Coordinating Research Council(CRC)
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Several participants in Phase 2 of the Air Quality Model Evaluation International Initiative (AQMEII-2) who are applying coupled models to the North American domain are comparing model results for two years: 2006 and 2010. While a key difference of interest between these two years from a modeling perspective are the large reductions in emissions of NOx (21%) and SO2 (36%) which occurred mostly in the eastern U.S., meteorological conditions also differed significantly between these two years and these differences both confound the impact of emission reductions on ambient air quality and provide an opportunity to examine how models respond to changing meteorology. Observed summer ozone levels in many portions of the Northeast and Midwest were largely unchanged in 2010 despite reductions in precursor emissions. The authors have previously demonstrated that normalization of the ozone trend to account for differences in meteorological conditions, including warmer summer temperatures in 2010, shows that the emission reductions would have resulted in lower ozone levels at these locations if not for the countervailing influence of meteorological conditions. We present here an evaluation of the ability of models to accurately account for the impact of the 2006 Ã¢â‚¬â€œ 2010 emission reductions on air quality using a synoptic weather pattern classification methodology designed to remove the influence of meteorology on the 2006 Ã¢â‚¬â€œ 2010 air quality trends. The synoptic classification consists of matching groups of days between the two years on the basis of similarities in sea-level pressure patterns. Results show that the models exhibit some skill in replicating observed ozone trends between 2006 and 2010 when results are stratified by synoptic patterns. However, the pattern classification, which is based solely on sea-level pressure, does not account for other key meteorological factors influencing ozone concentration differences between 2006 and 2010 and thus does not provide for a true evaluation of the modelÃ¢â‚¬â„¢s ability to replicate the underlying (emissions driven) ozone trend.