1. Long-range transport of NO y and ozone from Asia Thomas Walker Dalhousie University 3 rd GEOS-Chem Users' Meeting April 13, 2007

2. A North American context... [ppb] Average contribution over Canada and US is comparable (3.5 - 4 ppb) Asian contribution to surface O 3 in April 2006 [ppb]

3. Flights (Phase B): ● DC8 (10 flights) ● Hawaii, HI & Anchorage, AK ● C130 (12 flights) ● Seattle, WA ● Cessna (33 flights) ● Whistler, BC Measurements: DC8 – gas phase chemistry C130 – NO y, O 3, CO, AMS Cessna – O 3, CO, AMS

4. ● V7-04-10, GEOS4 ● Typical spinup: 9 months ● Modifications: ● scaled lightning NO x emissions above 30N to match 1.6 Tg/yr source [Martin, 2006] ● scaled Asian anthropogenic NO x emissions ● Studies: ● “No Asia” ● “No Lightning” ● “No PAN” ● Rn-Pb-Be simulation (12 month spinup) Use of GEOS-Chem 78% increase in anthropogenic emissions in China

5. Campaign average profiles Aircraft GC – Streets GC – Scaled GC – No Lightning GC – No Asia

6. Ozone Columns

7. LRT through PAN NO x at 2km, Apr-May avg NO x (with PAN) NO x (without PAN)

8. Model up-down ozone flux at tropopause [kg/s] April May

9. Diagnosing strat-trop exchange using Be-7 Campaign average, DC8 Measured Be-7 above 400hPa Modelled Be-7 above 400hPa

10. Atmospheric Composition Analysis Group: Randall Martin Bastien Sauvage Lok Lamsal Betty Carlin Rong-ming Hu Aaron van Donkelaar Neil Moore Gray O'Byrne Thanks to...

11. Summary ● Long-range transport does affect Canada ● Large change in emissions results in small change in transport ● Transport from Asia and lightning each contribute ~5 DU to ozone columns in western Canada, US ● Modelled Be7 can be used to diagnose strat-trop exchange ● Integrate IONS and WOUDC ozonesondes ● Differentiate between direct ozone transport and ozone production from PAN subsidence ● Attribution of modelled HNO3... dust? ● Improve emissions estimate using satellite inversion with OMI Future Plans

12. References Hudman, R.C. et al. Surface and lightning sources of nitrogen oxides over the United States: magnitudes, chemical evolution, and outflow. Submitted to JGR, 2007. Li, Q. et al. Stratospheric versus pollution influences on ozone at Bermuda: Reconciling past analyses. JGR, 2002. Martin, R.V. et al. Evaluation of space-based constraints on global nitrogen oxide emissions with regional aircraft measurements over and downwind of eastern North America. JGR, 2006. Moxim, W.J. et al. Simulated global tropospheric PAN: Its transport and impact on NOx. JGR, 1996.