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Constraints on the Production of Nitric Oxide by Lightning as Inferred from Satellite Observations

Constraints on the Production of Nitric Oxide by Lightning as Inferred from Satellite Observations. Randall Martin Dalhousie University. With contributions from Bastien Sauvage & Ian Folkins: Dalhousie Univeristy Christopher Sioris: Environment Canada

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Constraints on the Production of Nitric Oxide by Lightning as Inferred from Satellite Observations

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  1. Constraints on the Production of Nitric Oxide by Lightning as Inferred from Satellite Observations Randall Martin Dalhousie University With contributions from Bastien Sauvage & Ian Folkins: Dalhousie Univeristy Christopher Sioris: Environment Canada Christopher Boone and Peter Bernath: University of Waterloo Jerry Ziemke: NASA Goddard

  2. Global Lightning NOx Source Remains UncertainConstrain with Top-down Satellite Observations SCIAMACHY Tropospheric NO2 Columns ACE-FTS Limb HNO3 in Upper Troposphere OMI & MLS Both instruments onboard Aura satellite Tropospheric O3 Lightning: responsible for >35% of global OH & tropical tropospheric O3 Sauvage et al., 2007

  3. Current Estimate of Annual Global NOx SourcesAs Used In GEOS-Chem Lightning Global: 6.0 Tg N yr-1 Tropics: 4.4 Tg N yr-1 Other NOx sources: (fossil fuel, biofuel, biomass burning, soils) 39 Tg N yr-1 1010 molecules N cm-2 s-1

  4. Tropospheric NO2 Columns Retrieved from SCIAMACHY Nov - Apr NO/NO2  w Altitude May - Oct Retrieval Uncertainty ±(5x1014 molec cm-2 + 30%) Tropospheric NO2 (1015 molecules cm-2) Data from Martin et al., 2006

  5. Simplified Chemistry of Nitrogen OxidesExploit Longer Lifetimes in Upper Troposphere Upper Troposphere hv NO Ozone (O3) NO2 O3,RO2 lifetime ~ month NOx lifetime ~ week HNO3 lifetime ~ weeks NO/NO2  with altitude Boundary Layer hv NO2 Ozone (O3) NO O3,RO2 lifetime ~ days NOx lifetime < day HNO3 Nitrogen Oxides (NOx)

  6. Strategy 1) Use GEOS-Chem model to identify species, regions, and time periods dominated by the effects of lightning NOx production 2) Constrain lightning NOx source by interpreting satellite observations in those regions and time periods

  7. Simulated Monthly Contribution of Lightning, Soils, and Biomass Burning to NO2 Column Martin et al., 2007

  8. Annual Mean NO2 Column at Locations & Months with >60% from Lightning, <25% from Surface Sources SCIAMACHY (Uses 15% of Tropical Observations) Meridional Average GEOS-Chem with Lightning (6±2 Tg N yr-1) SCIAMACHY GEOS-Chem with Lightning (8% bias, r=0.75) GEOS-Chem without Lightning (-60% bias) GEOS-Chem without Lightning NO2 Retrieval Error ~ 5x1014 molec cm-2 Tropospheric NO2 (1014 molec cm-2) Martin et al., 2007

  9. ACE HNO3 over 200-350 hPa for Mar 2004 – Feb 2006 HNO3 Mixing Ratio (pptv) V2.2 reprocessed data

  10. GEOS-Chem Calculation of Contribution of Lightning to HNO3 HNO3 With Lightning (6±2 Tg N yr-1) Focus on 200-350 hPa Fraction of HNO3 from Lightning No Lightning HNO3 from Lightning Fraction from Lightning Jan Jul Martin et al., 2007

  11. Annual Mean HNO3 Over 200-350 hPa at Locations & Months with > 60% of HNO3 from Lightning ACE (Uses 72% of Tropical Measurements) Meridional Average GEOS-Chem with Lightning (6±2 Tg N yr-1) ACE-FTS v2.2 research ______ reprocessed - - GEOS-Chem with Lightning (-6% bias, r=0.81) GEOS-Chem without Lightning GEOS-Chem without Lightning (-77% bias) HNO3 Retrieval Error ~35 pptv Martin et al., 2007 +reprocessed HNO3 Mixing Ratio (pptv)

  12. OMI/MLS Tropospheric Ozone Column Jan Jul Data from Ziemke et al. (2006)

  13. Calculated Monthly Contribution of Lightning to O3 Column O3 Column from Lightning Column Fraction from Lightning Martin et al., 2007

  14. Annual Mean Tropospheric O3 Columns at Locations & Months with > 40% of Column from Lightning OMI/MLS (Uses 15% of Tropical Measurements) Meridional Average GEOS-Chem with Lightning (6±2 Tg N yr-1) GEOS-Chem with Lightning (-1% bias, r=0.85) OMI/MLS GEOS-Chem without Lightning (-45% bias) GEOS-Chem without Lightning O3 Retrieval Error < 5 Dobson Units Tropospheric O3 (Dobson Units) Martin et al., 2007

  15. Lightning NOx Dominant Source for Tropical Tropospheric Ozone Sensitivity to decreasing NOx emissions by 1% for each source 6 Tg N/yr 6 Tg N/yr DJF 6 Tg N/yr MAM JJA SON ΔDU Lightning Ozone Production Efficiency = 3 times OPE of each surface source Sauvage et al., 2007

  16. NOx ppb Injection of NOx (mostly from lightning) into the upper troposphere O3 production during transport and subsidence over South Atlantic basin Simulated Annual Mean Characteristics O3 ppb Sauvage et al., 2007

  17. Conclusions Global lightning NOx source likely between 4 – 8 Tg N / yr 6 Tg N / yr is a best estimate Further refinement will require - vertically-resolved constraint - more observations (e.g. HNO3) - improved satellite retrieval accuracy (e.g. NO2) - stronger constraints on midlatitude source - model development to better represent processes (e.g. lightning NOx representation, vertical transport) Acknowledgements CFCAS and NASA

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