Informing North American Background Informing North American - PowerPoint PPT Presentation

Slide 1 Slide 1 Informing North American Background Informing North American Background Ozone from Observations: Ozone from Observations: Ozone from Observations: Ozone from Observations: Characterizing Ozone Levels in Characterizing Ozone Levels in North America from Ozonesonde and North America from Ozonesonde and North America from Ozonesonde and North America from Ozonesonde and Surface Observations Surface Observations Sam Oltmans Sam Oltmans Boulder Colorado Boulder Colorado Boulder, Colorado Boulder, Colorado Comments to the U.S. EPA Comments to the U.S. EPA CASAC Ozone Review Panel CASAC Ozone Review Panel January 9, 2012 January 9, 2012

Slide 2 Slide 2 What can observations tell us about Wh t What can observations tell us about Wh t b b ti ti t ll t ll b b t t background ozone? background ozone?  We don’t measure North American We don’t measure North American Background (NAB) ozone Background (NAB) ozone So what do we measure? So what do we measure?  Can we measure “background” ozone at Can we measure “background” ozone at a North American location like Trinidad a North American location like Trinidad H Head, California? Head, California? H d C lif d C lif i ? i ?  What are the characteristics of North What are the characteristics of North A American “background” ozone? American “background” ozone? A i i “b “b k k d” d” ? ?

Slide 3 Slide 3 Location of the NOAA Location of the NOAA Trinidad Head Observatory Trinidad Head Observatory Conclusion: Trinidad Conclusion: Trinidad Head is a well Head is a well exposed site in a exposed site in a exposed site in a exposed site in a relatively remote relatively remote location. location.

Slide 4 Slide 4 Surface (daytime) Surface (daytime) and profile ozone and profile ozone and profile ozone and profile ozone at Trinidad Head at Trinidad Head Diamond = Mean Diamond = Mean Horizontal/ Vertical Line I nside Box = Median Box = I nner 50 th Percentile (25th & 75th) (25th & 75th) Whiskers = I nner 90 th Percentile (5th & 95th) Red = Surface Values Superimposed on the Profile. Superimposed on the Profile. Conclusion: Conclusion: 1) 1) Average spring daytime Average spring daytime (or 8 (or 8- ( ( -hr max) surface hr max) surface ) ) ozone at Trinidad Head ozone at Trinidad Head is ~43 ppb. 25% of the is ~43 ppb. 25% of the hourly hourly avgs avgs. >45 ppb. . >45 ppb. 2) Above the boundary 2) 2) Above the boundary 2) Above the boundary Above the boundary layer (~2 km) avg. O layer (~2 km) avg. O 3 is is ≥ 50 ppb in ≥ 50 ppb in spring spring and and summer. summer.

April Slide 5 I s ozone measured at Trinidad Head I s ozone measured at Trinidad Head Representative of PRB conditions? Representative of PRB conditions? Representative of PRB conditions? Representative of PRB conditions? Back trajectories (10 Back trajectories (10- -day) to Trinidad Head for day) to Trinidad Head for days in April with hourly days in April with hourly avgs avgs. . ≥ 50 50 ppbv ppbv Trinidad Head surface T i id d H d f ozone separated by day (10-21 LST - red) and night (22-09 LST - blue). August Conclusion: During the daytime – Conclusion: During the daytime Conclusion: During the daytime Conclusion: During the daytime Very frequently. Very frequently. At night At night – – Some of the time. Some of the time.

Slide 6 Slide 6 Wh t d Wh t d What do vertical What do vertical ti ti l l profiles say profiles say about ozone about ozone reaching the reaching the California California coast? coast? coast? coast? Vertical profiles of carbon monoxide measured in flasks measured in flasks collected on aircraft flights above Trinidad Head CA. The green pts Average ozone mixing ratio Average ozone mixing ratio give the individual obs profiles at four sites making profiles at four sites making and the red circles and the red circles ozonesonde ozonesonde observations observations indicate avgs and during the IONS 2010 during the IONS 2010- -CalNex CalNex standard deviations . Campaign in May Campaign in May- -June 2010. June 2010. Conclusion: Air Conclusion: Air Conclusion: In the lower Conclusion: In the lower flowing into Trinidad flowing into Trinidad flowing into Trinidad flowing into Trinidad troposphere (<4 km) average troposphere (<4 km) average Head represents the Head represents the ozone amounts are similar ozone amounts are similar Pacific Pacific “background” “background”. along the California coast. along the California coast.

What influences tropospheric ozone What influences tropospheric ozone Slide 7 levels at the California coast? levels at the California coast? TH = Trinidad Head RY = Point Reyes Conclusion (below): Conclusion (below): PS = Point Sur 1) Strat 1) Strat contribution contribution Conclusion (left Conclusion (left SN = San Nicolas I sl. increases at lower increases at lower increases at lower increases at lower panel): North panel): North panel): North panel): North levels moving levels moving American influence American influence south. south. has an insignificant has an insignificant 2) 2) Asian transport is Asian transport is impact on lower impact on lower f lt felt most strongly felt most strongly f lt t t t t l l trop trop O3 levels along O3 levels along above the boundary above the boundary the coast of CA. the coast of CA. layer (~2 km) layer (~2 km) Tropsopheric Ozone T h i O Stratospheric St t h i A i Asian Transport T t (ppbv) Contribution (% ) (NOx Tracer – ppb)

What can interior sites in North America What can interior sites in North America Slide 8 tell us about NAB? tell us about NAB? Fire Counts April 2008 14-20 April 2008 I nfluence of Eurasian Biomass Burning Surface ozone at Denali NP, AK in April 2008. Peak hourly avg 78 ppb, 8-hr max of 75 ppb, 5-day avg > 65 ppb associated with 5 d 65 b i t d ith trajectory and ancillary constituents showing likely cause as major early fires in Eurasia. Conclusion: During spring Asian transport can have significant influence on lower trop O3 levels. Higher spring ozone amounts (April avg. g p g ( p g ~ 45 ppb) have little North American influence and likely represent ozone levels of air flowing into North America.

Slide 9 Slide 9 Comparison of Comparison of Observations with Observations with Observations with Observations with Model Results Model Results Comparison of model results from the GFDL AM3 with observations the GFDL AM3 with observations over the western US in May-June 2010. From Lin et al. Note the important contribution (in preparation) from the stratosphere especially from the stratosphere, especially relative to the Asian contribution and the contribution from NAB to the observed O 3 above 50 ppb. Comparison of model results C i f d l lt Diamonds are Trinidad ozonesondes. Blue from the high resolution symbols are the GEOS Chem Model (Zhang seasonal surface ozone average at Trinidad et al., 2011) and Head. Red symbols are the Mt Bachelor the Mt. Bachelor observations at Trinidad b ti t T i id d seasonal average Head and Mt. Bachelor, OR plotted at the altitude of the observatory. Profile (McDonald-Buller et al., results from the GEOS- 2011). Chem model for 2006 are shown as green g Th The modeled O 3 and d l d O d pluses. The contribution from PRB the model background O 3 are generally profile is shown by less than the observed orange circles. (McDonald-Buller et al., value. 2011).