1. CANADIAN, MEXICAN, AND INTERCONTINENTAL INFLUENCES ON U.S. AIR QUALITY Daniel J. Jacob with Rokjin J. Park 1, Helen Wang, Philippe H. LeSager, Lin Zhang and funding from EPRI, DOE, NASA 1 now at Seoul National University

2. THE U.S. EPA REGIONAL HAZE RULE Mean visibility degradation (deciviews) at IMPROVE sites, 2001 Reduce U.S. aerosol sources to improve visibility in wilderness areas: progress must follow a linear rate toward endpoint of natural visibility by 2064 Park et al. [AE 2006] 1 o x1 o

3. NATURAL vs. BACKGROUND VISIBILITY DEGRADATION Deciviews 2001 observationsNatural Background; includes transboundary pollution  g m -3 Natural: shut off anthropogenic emissions worldwide Background: shut off anthropogenic emissions in U.S. only Park et al. [AE 2006] >70% of transboundary pollution is from Canada and Mexico Model simulations

4. DIFFERENT DEFINITIONS OF THE U.S. OZONE BACKGROUND GEOS-Chem 1 o x1 o simulation All slides show max daily 8-h surface ozone for June-August 2001 N. American background Zero anthropogenic emissions in N. America Used by EPA as policy- relevant background (PRB) U.S. background Zero anthropogenic emissions in U.S. only Wang et al. [AE, submitted] Mean JJA values

5. CANADIAN/MEXICAN OZONE POLLUTION ENHANCEMENT as computed by difference of N. American and U.S. backgrounds Circles are CASTNET/AQS rural sites used for model evaluation Mean Canadian/Mexican enhancements are 1-3 ppb over most of U.S.; much larger enhancements in border areas of Northeast (up to 15 ppb), Southwest (up to 13 ppb) Canadian emissions from CAC (2005), Mexican emissions from BRAVO (1999) Wang et al. [AE, submitted] Mean June-August 2001 values (months when Can/Mex influence is maximum)

6. Boersma et al. [JGR 2008] TROPOSPHERIC NO 2 FROM OMI October 2004 U.S. NEI 99 Canada CAC 05 Mexico BRAVO 99 Anthropogenic NO x emissions Tg N a -1 6.70.760.93 Most Canadian emissions are close to U.S. border: not so for Mexico

7. MODEL EVALUATION FOR CANADIAN/MEXICAN INFLUENCE Time series at the sites most affected Ozone, ppb Jun Jul Aug Whiteface Mtn. Base, NY Observations Model (standard) observed O 3 >75 ppb with >10 ppb from Canada/Mexico Wang et al. [AE, submitted] US background NA background (PRB) Canada + Mexico Unionville, MichiganAlpine, California

8. BACKGROUND CORRELATION WITH OZONE Background concentration statistics for NE and SW sites in 10-ppb ozone bins max 75th med 25th min North American background U.S. background 1:1 model vs. obs. line Wang et al. [AE, submitted] An air quality standard as low as 60 ppb would be achievable with domestic emission reductions alone Northeast Southwest

9. AREAS WHERE CANADIAN/MEXICAN INFLUENCES CONTRIBUTE MOST TO EXCEEDANCES OF U.S. AIR QUALITY STANDARD # model days in JJA 2001 where ozone >75 ppb and Can/Mex influence > 10 ppb Largest effects around the Great Lakes, eastern seaboard, and S. California Wang et al. [AE, submitted]

10. LOOKING AHEAD TO 2020 Global CLE inventory + CAIR for U.S. Anthropogenic NO x emissions  by 51% in U.S., 49% in Canada, 34% in Mexico …but CLE inventory has high emissions in southeastern Canada! Canadian pollution influence in Northeast U.S. in 2020 is comparable to or greater than residual influence from U.S. power plants (18% of U.S. NO x emissions in 2020) Summer mean Canadian/Mexican pollution enhancement (2020) Wang et al. [AE, submitted]

11. NASA/INTEX-B AIRCRAFT CAMPAIGN (APR-MAY 2006) Validate, augment, and exploit satellite observations of transpacific transport DC-8 C-130 Honolulu Anchorage Seattle

12. TES and AIRS satellite observations of a transpacific plume CO columns TESGEOS-ChemAIRS Zhang et al. [ACP, submitted] DC-8 track A B

13. USING OZONE-CO CORRELATIONS FROM TES TO DETECT TRANSPACIFIC OZONE POLLUTION Zhang et al. [ACP, submitted]

14. Transpacific Plume observed by DC-8 on May 9 th B-south branch HNO 3 NO O3O3 CO Solid: observations Dash: GEOS-Chem A-north branch PAN CO O3O3 PAN Backward and forward trajectories for the plume Ozone is produced in the S-branch following subsidence and decomposition of PAN to NO x Most of this ozone circles around the Pacific High and becomes the “river of pollution” to the western equatorial Pacific (PEM-Tropics B); only a small fraction reaches the western U.S. A B “river of pollution” Zhang et al. [ACP, submitted]

15. SOURCE ATTRIBUTION OF OZONE USING MODEL ADJOINTS GEOS-Chem adjoint simulation for INTEX- B period (Apr-May 2006) Contribution of ozone production regions to ozone concentration at Mt. Batchelor Observatory 23% 21% 17% 6% Mean East Asian pollution enhancement of 9.2 ppb at MBO includes 5.6 ppb from China and 3.6 ppb from Japan+Korea Zhang et al. [in prep.]