title: Interannual Variability in Baseline Ozone and Its Relationship to Surface Ozone in the Western U.S.
abstract: Baseline ozone refers to observed concentrations of tropospheric ozone at sites that have a negligible influence from local emissions. The Mount Bachelor Observatory (MBO) was established in 2004 to examine baseline air masses as they arrive to North America from the west. In May 2012, we observed an O3 increase of 2.0-8.5 ppbv in monthly average maximum daily 8-hour average O3 mixing ratio (MDA8 O3) at MBO and numerous other sites in the western U.S. compared to previous years. This shift in the O3 distribution had an impact on the number of exceedance days. We also observed a good correlation between daily MDA8 variations at MBO and at downwind sites. This suggests that under specific meteorological conditions, synoptic variation in O3 at MBO can be observed at other surface sites in the western U.S. At MBO, the elevated O3 concentrations in May 2012 are associated with low CO values and low water vapor values, consistent with transport from the upper troposphere/lower stratosphere (UT/LS). Furthermore, the Real-time Air Quality Modeling System (RAQMS) analyses indicate that a large flux of O3 from the UT/LS in May 2012 contributed to the observed enhanced O3 across the western U.S. Our results suggest that a network of mountaintop observations, LiDAR and satellite observations of O3 could provide key data on daily and interannual variations in baseline O3.
authors.affiliation: Department of Atmospheric Sciences, University of Washington , 408 Atmospheric Sciences-Geophysics Building, Seattle, Washington 98195, United States.
authors.forename: Pao M
authors.initials: PM
authors.lastname: Baylon
authors.affiliation: Department of Atmospheric Sciences, University of Washington , 408 Atmospheric Sciences-Geophysics Building, Seattle, Washington 98195, United States.|School of Science, Technology, Engineering and Mathematics, University of Washington Bothell , 18115 Campus Way NE, Bothell, Washington 98011, United States.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Jaffe
authors.affiliation: NOAA/NESDIS , Center for Satellite Applications and Research, Advanced Satellite Products Branch, 1225 West Dayton Street, Madison, Wisconsin 53705, United States.
authors.forename: R Bradley
authors.initials: RB
authors.lastname: Pierce
authors.affiliation: Department of Natural Resources and Environmental Science, University of Nevada-Reno , Reno, Nevada 89557, United States.
authors.forename: Mae S
authors.initials: MS
authors.lastname: Gustin
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry; D004784:Environmental Monitoring; D010126:Ozone / Q000737:chemistry*; D013997:Time Factors; D014481:United States
chemical_list: D000393:Air Pollutants; D010126:Ozone