1. INTERCONTINENTAL INFLUENCES ON OZONE AND AEROSOL AIR QUALITY Daniel J. Jacob Harvard University NO x emissions (2000) with Colette L. Heald, Rokjin Park, Rynda C. Hudman, Solene Turquety and support from NASA, NOAA, EPA, EPRI

2. TREND IS TOWARD TIGHTER AIR QUALITY STANDARDS AOT40 ozone growing season standard for Europe: daytime ppb-hours above 40 ppbv over growing season Standards: 10,000 ppbh (forests) 3,000 ppbh (crops) … correspond to mean ozone concentration of 41-45 ppbv EMEP [2005] Current 8-h average ozone standards: 84 pppbv (U.S.), 55 ppbv (EU) AOT40

3. REGIONAL HAZE RULE IN THE UNITED STATES: national parks to achieve “natural visibility” by 2064 clean daymoderately polluted day Acadia National Park, Maine visibility (deciviews) Schedule for implementation of Regional Haze Rule [U.S. EPA, 2001] 2004 2018 2064 Anthropogenic emissions (illustrative) YEAR

4. U.S. VISIBILITY IMPAIRMENT BY ASIAN DUST STORMS Glen Canyon, Arizona clear dayApril 16, 2001: Asian dust! … anthropogenic pollution is transported together with the dust Colette Heald (Harvard) satellite data Aerosol optical depth (AOD)Carbon monoxide (CO) MODIS satellite datamodel (dust) model (sulfate) MOPITT satellite data

5. PATHWAYS FOR INTERCONTINENTAL TRANSPORT Stohl and Eckhard [2004] Transparent arrows: transport in boundary layer below 2 km Colored arrows: transport in free troposphere

6. TWO MODES OF INTERCONTINENTAL INFLUENCE AsiaN. America Europe Boundary layer Free troposphere liftingsubsidence boundary layer advection Tropopause HEMISPHERIC POLLUTION BACKGROUND “Direct” intercontinental transport Mixing Direct intercontinental transport: fast (~1 week) transport from source to receptor continent; either by boundary layer advection or by lifting to lower free troposphere followed by subsidence Hemispheric pollution: pollution mixes in free troposphere, affecting free tropospheric background, in turn affecting surface concentrations by subsidence 2 km

7. GLOBAL DISTRIBUTION OF TROPOSPERIC OZONE OBSERVED FROM THE GOME SATELLITE INSTRUMENT X. Liu, Harvard SAO/CFA Mean JJA 1997 tropospheric columns (Dobson Units): circumpolar transport around northern midlatitudes pollution belt

8. OZONE BACKGROUND AT NORTHERN MID-LATITUDES HAS A LARGE ANTHROPOGENIC COMPONENT Observations at free tropospheric mountain sites in Europe [Marenco et al., 1994] Preindustrial model ranges AOT40 std European 8-h std. stratospheric constribution 0 10 20 30 40 50 60 1870 1890 1910 1930 1950 1970 1990

9. GEOS-Chem GLOBAL 3-D MODEL OF ATMOSPHERIC TRANSPORT AND CHEMISTRY driven by GEOS assimilated meteorological observations from NASA Global Modeling and Assimilation Office (GMAO); native resolution 1 o x1 o (  2 o x2.5 o ), ~50 vertical levels cross-tropopause transport constrained globally from observations (400 Tg O 3 yr -1 ) Coupled tropospheric ozone-aerosol chemistry (~100 interacting species) Ozone precursors: Nitrogen oxides (NO x ): combustion, lightning, soils Methane: wetlands, agriculture, natural gas, coal mining Nonmethane volatile organic compounds (NMVOCs): vegetation, combustion, industry Carbon monoxide (CO): combustion, VOC oxidation Aerosols and precursors: Sulfur gases: combustion, oceans, volcanoes, biomass burning Nitrogen oxides Ammonia: agriculture, soils, biomass burning, oceans Organic carbon (OC): biomass burning, vegetation, industry Black carbon (BC): combustion Soil dust, sea salt

10. MEAN SURFACE OZONE ENHANCEMENTS FROM ANTHROPOGENIC NO x AND NMVOC EMISSIONS IN DIFFERENT CONTINENTS GEOS-Chem model, July 1997 North America Europe Asia Li et al. [2002] as determined from sensitivity simulations with these sources shut off

11. INTERCONTINENTAL OZONE ENHANCEMENTS ARE LARGER IN FREE TROPOSPHERE THAN AT SURFACE Mean GEOS-Chem ozone enhancements at 45 o N in summer from anthropogenic emissions of NO x and NMVOCs in different continents N America EuropeAsia N. American emissions European emissions Asian emissions Li et al. [2002]

12. Fiore et al. [2002] SUMMERTIME VARIABILITY OF OZONE INTERCONTINENTAL POLLUTION ENHANCEMENT IN U.S. tropical air Subsidence of Asian pollution + local production stagnation Effect is maximum for ozone concentrations in mid-range (40-70 ppbv) GEOS-Chem summer statistics of surface afternoon ozone enhancements from Asian and European emissions over ensemble of U.S. surface sites

13. EFFECT OF NORTH AMERICAN SOURCES ON EXCEEDANCES OF EUROPEAN AIR QUALITY STANDARD (55 ppbv, 8-h average) GEOS-CHEM model results, summer 1997 Number of exceedance days (out of 92) # of exceedance days that would not have been in absence of N.American emissions Li et al. [2002]

14. PROBING TRANSPACIFIC POLLUTION TRANSPORT High-ozone Asian pollution plumes and stratospheric influence observed in lower free troposphere … but not at surface CO O3O3 PAN HNO 3 May 5 plume at 6 km: High CO and PAN, no O 3 enhancement May 17 subsiding plume at 2.5 km: High CO and O 3, PAN  NO x  HNO 3 Hudman et al. [2004] Observations by D. Parrish, J. Roberts, T. Ryesrson (NOAA/AL) NOAA/ITCT-2K2 aircraft campaign, April-May 2002

15. CONCEPTUAL PICTURE OF OZONE PRODUCTION IN TRANSPACIFIC ASIAN POLLUTION PLUMES NO x HNO 3 PAN Asian boundary layer (OPE ~ 5) PAN, weak  O 3 Warm conveyor belt; 5-10% export of NO y mainly as PAN strong  O 3 Subsidence Over E Pacific OPE 60-80 PAN  NO x  HNO 3 U.S. boundary layer  O 3 = 6 ± 2 ppbv (California) 10x dilution (Asian dust data) E. Asia Pacific United States Hudman et al. [2004] Stratospheric downwelling GEOS-CHEM ozone production efficiency (2-4 km)

16. CALIFORNIA MOUNTAIN SITES ARE MOST SENSITIVE TO ASIAN OZONE POLLUTION …because there is less dilution Observed 8-h ozone at Sequoia National Park (1800 m) in May 2002 vs. corresponding simulated (GEOS-CHEM) Asian pollution ozone enhancement Asian enhancements are 6-10 ppbv during exceedances of standard; unlike at surface sites, Asian pollution influence is not minimum under high-ozone conditions! May 17 obs. Asian plume event in red Hudman et al. [2004]

17. ICARTT: COORDINATED ATMOSPHERIC CHEMISTRY CAMPAIGN OVER EASTERN NORTH AMERICA AND NORTH ATLANTIC IN SUMMER 2004 International, multi-agency (U.S.) collaboration targeted at U.S. regional air quality, pollution outflow, transatlantic transport, aerosol radiative forcing Terra ERS MISR, MODIS, MOPITT ERS-2 GOME Envisat SCIAMACHY Aqua AIRS, MODIS NASA DC-8 UK BAE-143 DLR Falcon NOAA-P3 DOE G-1 NASA Proteus

18. AIRS CO SATELLITE OBSERVATIONS OF INTERCONTINENTAL TRANSPORT DURING ICARTT Asian pollution U.S. pollution Alaskan fires Wallace McMillan (UMBC) Carbon monoxide (CO) columns on July 18

19. ASIAN POLLUTION PLUME OVER EASTERN U.S. sampled by NASA aircraft on July 15 Observed  O 3 = 20-40 ppbv,  CO = 20 ppbv GEOS-Chem  O 3 = 5-10 ppbv,  CO = 10-20 ppbv High Halon-1211 in plume confirms Asian origin GEOS forecast Asian CO (9 km) Observed O 3 (ppbv) Observed CO (ppbv)

20. TRANSPACIFIC TRANSPORT OF AEROSOLS Colette L. Heald, Harvard MODIS satellite observations of aerosol optical depth (AOD) in different seasons, and corresponding GEOS-Chem model simulations DJF MAM JJA SON MODIS AOD GEOS-CHEM AOD: Asian anthrop. Dust

21. AIRCRAFT OBSERVATIONS IN ASIAN WARM CONVEYOR BELT (WCB) OUTFLOW ILLUSTRATE SCAVENGING OF AEROSOLS DURING LIFTING TO FREE TROPOSPHERE Longitude Data from E.V. Browell boundary layer outflow WCB outflow Ozone: WCB outflow Aerosols scavenged from WCB outflow TRACE-P campaign out of Hong Kong and Japan, spring 2001

22. P3B DATA over NW Pacific (30 – 45 o N, 120 – 140 o E) SCAVENGING OF AEROSOLS INCLUDING BLACK CARBON (BC) APPARENT IN MEAN VERTICAL PROFILES Park et al. [2005] TRACE-P observations over NW Pacific and GEOS-Chem simulations Sulfate is most important exported anthropogenic aerosol in model

23. MYSTERY ORGANIC AEROSOL IN HIGH-ALTITUDE ASIAN OUTFLOW ACE-Asia aircraft observations over Japan (spring 2001) Elemental carbon (EC) observed GEOS-Chem Organic carbon (OC) implies large secondary production in free troposphere not included in present models; Dominates aerosol loading in free troposphere; could produce large negative radiative forcing effect (~ 1W m -2 ) Colette Heald (Harvard) (A.D. Clarke)

24. INTERCONTINENTAL TRANSPORT OF ASIAN AND NORTH AMERICAN ANTHROPOGENIC SULFATE As determined from GEOS-Chem 2001 sensitivity simulations with these sources shut off Intercontinental enhancements of anthropogenic sulfate over U.S. are of same order as interstate enhancement threshold used for regulation (0.2  g m -3 ) and higher than EPA estimates of natural values (0.1  g m -3 )

25. VERTICAL STRUCTURE OF TRANSPACIFIC TRANSPORT GEOS-Chem model results for spring 2001 (15-45 o N) C.L. Heald, Harvard Asian CO Asian sulfate Asia N. America Asia N. America Asian aerosols are transported in lower free troposphere and subside over the NE Pacific; topography in western U.S. promotes contact with surface

26. EVIDENCE OF ASIAN SULFATE IN IMPROVE NETWORK OF AEROSOL MEASUREMENTS AT U.S. SITES NW US: 0.72 μgm -3 NW US: 1.04 μgm -3 NW US: 0.60 μgm -3 spring 2001 mean 24-h seasonal max GEOS-Chem Asian influence NW US: 0.18 μgm -3 IMPROVE GEOS-CHEM Asian anthr (GEOS-Chem) March 1 April 1 May 1 June 1 Time series over NW U.S. (spring 01) IMPROVE data: spring 2001 mean days of GEOS-Chem 24-h seasonal max 1.4  g m -3

27. Janus mission proposed to NASA: GLOBAL MAPPING OF ATMOSPHERIC COMPOSITION FROM L1 ORBIT Global mapping of tropospheric aerosols, clouds, NO 2, HCHO, SO 2, CO, CO 2 : observe transport on regional to global scales Continuous observation of Earth’s sunlit disk with 5 km nadir horizontal resolution