1. Analysis of Satellite Observations to Estimate Production of Nitrogen Oxides from Lightning Randall Martin Bastien Sauvage Ian Folkins Chris Sioris Chris Boone Peter Bernath University of Saskatchewan Jerry Ziemke

2. Global Lightning NOx Emissions Remain Poorly Constrained (1–13 Tg N/yr) Flashes km -2 min -1 DJF JJA 10-year Mean Flash Rate from the OTD & LIS Satellite Instruments Global rate 44±5 flash/sec [Christian et al. 2003] 30 – 400 moles NO per flash

3. Top-down Information from the SCIAMACHY, ACE, OMI, and MLS Satellite Instruments SCIAMACHY Aug 2002-present Nadir spatial resolution 60x30 km 2 Tropospheric NO 2 Columns (Martin et al., in press) ACE-FTS Jan 2004-present Limb Measurements in the Upper Troposphere High Resolution FTS (33 species) HNO 3 (Bernath et al., 2005; Boone et al., 2005) OMI & MLS Aug 2004-present Both instruments onboard Aura satellite OMI nadir UV-Vis, 24x13 km 2 with daily global coverage MLS thermal emission microwave limb sounder Tropospheric O 3 (Ziemke et al., in press)

4. Current Estimate of Annual Global NOx Emissions 10 10 molecules N cm -2 s -1 Lightning 6 Tg N yr -1 Other NOx sources: (fossil fuel, biofuel, biomass burning, soils) 39 Tg N yr -1

5. Tropospheric NO 2 Columns Retrieved from SCIAMACHY Retrieval Uncertainty ±(5x10 14 molec cm -2 + 30%) Martin et al., in press Tropospheric NO 2 (10 15 molecules cm -2 ) Nov - Apr May - Oct NO / NO2   w Altitude

6. Simplified Chemistry of Nitrogen Oxides Exploit Longer Lifetimes in Upper Troposphere NO NO 2 NOx lifetime < day Nitrogen Oxides (NO x ) Boundary Layer NO / NO2   with altitude hv NO NO 2 O 3, RO 2 hv HNO 3 NOx lifetime ~ week lifetime ~ weeks Ozone (O 3 ) lifetime ~ month Upper Troposphere Ozone (O 3 ) lifetime ~ days HNO 3 O 3, RO 2

7. Strategy 1) Use chemical transport model to identify species, regions, and time periods dominated by the effects of lightning NOx emissions 2) Constrain lightning NOx emissions by interpreting satellite observations in those regions and time periods GEOS-Chem Chemical Transport Model Assimilated Meteorology (NASA GMAO) 2 o x2.5 o horizontal resolution, 30 vertical layers O 3 -NO x -VOC chemistry Lightning: 6 Tg N/yr, Price and Rind (1992), Pickering et al. (1998) Aerosols: SO 4 2- -NO 3 - -NH 4 + -H 2 O, dust, sea-salt, carbonaceous Bey et al., 1999 Fiore et al., 2002 Martin et al., 2002, 2003 Park et al., 2003, 2004 41 tracers ~90 species 300 reactions

8. Calculated Monthly Contribution of Lightning and Soils to NO 2 Column Column Fraction from Lightning (6 Tg N / yr) Column Fraction from Soils (6 Tg N / yr) Unitless Jan Jul Jan Jul GEOS-Chem Tropospheric NO 2 Column 10 15 molec cm -2

9. Annual Mean Tropospheric NO 2 at Locations & Months with >50% of Column from Lightning and 50% of Column from Lightning and <25% from Soils Meridional Average SCIAMACHY (Uses 30% of Tropical Observations) GEOS-Chem with Lightning (-18% bias, r=0.75) GEOS-Chem without Lightning (-72% bias, r=0.70) Tropospheric NO 2 (10 14 molec cm -2 ) NO 2 Retrieval Error < 5x10 14 molec cm -2 GEOS-Chem with Lightning (6±2 Tg N yr -1 ) SCIAMACHY GEOS-Chem without Lightning

10. ACE HNO 3 over 200-300 hPa for Jan 2004 – Feb 2006 HNO 3 Mixing Ratio (pptv) Data from Boone et al., 2005

11. GEOS-Chem Calculation of Contribution of Lightning to HNO 3 HNO 3 from LightningFraction from Lightning ΔpptvUnitless Focus on 200-300 hPa HNO 3 With Lightning (6±2 Tg N yr -1 ) No Lightning Fraction of HNO 3 from Lightning Jan Jul

12. Annual Mean HNO 3 Over 200-300 hPa at Locations & Months with > 60% of HNO 3 from Lightning Smoothed Meridional Average ACE (Uses 70% of Tropical Measurements) GEOS-Chem with Lightning (-1% bias, r=0.74) GEOS-Chem without Lightning (-79% bias, r=0.15) HNO 3 Mixing Ratio (pptv) ACE GEOS-Chem with Lightning (6±2 Tg N yr -1 ) GEOS-Chem without Lightning HNO 3 Retrieval Error ~35 pptv

13. OMI/MLS Tropospheric Ozone Column Jan Jul Dobson units Data from Ziemke et al. (in press)

14. Calculated Monthly Contribution of Lightning to O 3 Column O 3 Column from Lightning Column Fraction from Lightning ΔDobson Units Unitless Jan Jul

15. Annual Mean Tropospheric O 3 Columns at Locations & Months with > 40% of Column from Lightning Meridional Average OMI/MLS (Uses 25% of Tropical Measurements) GEOS-Chem with Lightning (4% bias, r=0.70) GEOS-Chem without Lightning (-42% bias, r=0.70) Tropospheric O 3 (Dobson Units) OMI/MLS GEOS-Chem with Lightning (6±2 Tg N yr -1 ) GEOS-Chem without Lightning O 3 Retrieval Error < 5 Dobson Units

16. Conclusions Global lightning NOx emissions are likely between 4 – 8 Tg N / yr 6 Tg N / yr is a best estimate Further refinement will require - improved satellite retrieval accuracy (i.e. NO 2 ) - more observations (i.e. HNO 3 ) - model development to better represent processes (i.e. soil NOx, vertical transport, ice uptake of HNO 3 ) Acknowledgements National Aeronautics and Space Administration (NASA) Natural Sciences and Engineering Research Council of Canada (NSERC)