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Long-range transport of NOy and ozone from Asia

Thomas Walker

Dalhousie University

3rd GEOS-Chem Users' Meeting

April 13, 2007

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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]

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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 – NOy, O3, CO, AMS

Cessna – O3, CO, AMS

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  • 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

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Campaign average profiles

Aircraft

GC – Streets

GC – Scaled

GC – No Lightning

GC – No Asia

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Ozone Columns

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LRT through PAN

NOx at 2km, Apr-May avg

NOx (with PAN)

NOx (without PAN)

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Model up-down ozone flux at tropopause

[kg/s]

April

May

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Diagnosing strat-trop exchange using Be-7

Campaign average, DC8

Measured Be-7 above 400hPa

Modelled Be-7 above 400hPa

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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...

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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

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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.

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