Long-range transport of NOy and ozone from Asia

Thomas WalkerDalhousie University3rd GEOS-Chem Users' MeetingApril 13, 2007

A North American context...

[ppb]

Average contribution over Canada and US is comparable (3.5 - 4 ppb)

Asian contribution to surface O3 in April 2006

[ppb]

Flights (Phase B):● DC8 (10 flights)

● Hawaii, HI & Anchorage, AK

● C130 (12 flights)● Seattle, WA

● Cessna (33 flights)● Whistler, BC

Measurements:DC8 – gas phase chemistryC130 – NOy, O3, CO, AMSCessna – O3, CO, AMS

● V7-04-10, GEOS4● Typical spinup: 9 months● Modifications:

●scaled lightning NOx emissions above 30N to match 1.6 Tg/yr source [Martin, 2006]●scaled Asian anthropogenic NOx 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

Campaign average profilesAircraftGC – StreetsGC – ScaledGC – No LightningGC – No Asia

Ozone Columns

LRT through PAN

NOx at 2km, Apr-May avg

NOx (with PAN)NOx (without PAN)

Model up-down ozone flux at tropopause

[kg/s]

April

May

Diagnosing strat-trop exchange using Be-7

Campaign average, DC8

Measured Be-7 above 400hPa

Modelled Be-7 above 400hPa

Atmospheric Composition Analysis Group:Randall Martin

Bastien SauvageLok LamsalBetty Carlin

Rong-ming HuAaron van Donkelaar

Neil MooreGray O'Byrne

Thanks to...

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

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.