Global Production of Nitric Oxide by Lightning Inferred from Satellite Observations
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Transcript of Global Production of Nitric Oxide by Lightning Inferred from Satellite Observations
Global Production of Nitric Oxide by Lightning Inferred from Satellite Observations
Randall Martin
Dalhousie University
With contributions from
Bastien Sauvage & Ian Folkins: Dalhousie Univeristy
Christopher Sioris: University of Saskatchewan
Christopher Boone and Peter Bernath: University of Waterloo
Jerry Ziemke: NASA Goddard
Global Lightning NOx Source Remains UncertainGlobal Lightning NOx Source Remains Uncertain(1–20 Tg N/yr) (1–20 Tg N/yr)
Constrain with Top-down Satellite ObservationsConstrain with Top-down Satellite Observations
SCIAMACHY Tropospheric NO2 Columns
ACE-FTS Limb HNO3 Measurements in the Upper Troposphere
OMI & MLSBoth instruments onboard Aura satelliteTropospheric O3
Current Estimate of Annual Global NOx SourcesCurrent Estimate of Annual Global NOx Sources
1010 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
Tropospheric NOTropospheric NO22 Columns Retrieved from SCIAMACHY Columns Retrieved from SCIAMACHY
Retrieval Uncertainty
±(5x1014 molec cm-2 + 30%)
Tropospheric NO2 (1015 molecules cm-2)
Nov - Apr
May - Oct
NO/NO2
w Altitude
Data from Martin et al., 2006
Simplified Chemistry of Nitrogen OxidesSimplified Chemistry of Nitrogen OxidesExploit Longer Lifetimes in Upper TroposphereExploit Longer Lifetimes in Upper Troposphere
NO NO2
NOx lifetime < day
Nitrogen Oxides (NOx)
BoundaryLayer
NO/NO2
with altitude
hv
NO NO2
O3, RO2
hv
HNO3
NOx lifetime ~ week
lifetime ~ weeks
Ozone (O3)lifetime ~ month
Upper Troposphere
Ozone (O3)
lifetime ~ days
HNO3
O3, RO2
StrategyStrategy
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
Simulated Monthly Contribution of Lightning, Soils, and Simulated Monthly Contribution of Lightning, Soils, and Biomass Burning to NOBiomass Burning to NO22 Column Column
Annual Mean NOAnnual Mean NO22 Column at Locations & Months with >60% Column at Locations & Months with >60%
from Lightning, <25% from Surface Sourcesfrom Lightning, <25% from Surface Sources
Meridional Average
SCIAMACHY (Uses 15% of Tropical Observations)
GEOS-Chem with Lightning (8% bias, r=0.75)
GEOS-Chem without Lightning (-60% bias)
Tropospheric NO2 (1014 molec cm-2)
NO2 Retrieval Error ~ 5x1014 molec cm-2
GEOS-Chem with Lightning (6±2 Tg N yr-1)
SCIAMACHY
GEOS-Chem without Lightning
ACE HNOACE HNO33 over 200-350 hPa for Feb 2004 – Feb 2006 over 200-350 hPa for Feb 2004 – Feb 2006
HNO3 Mixing Ratio (pptv)
Data from Boone et al., 2005
GEOS-Chem Calculation of Contribution of Lightning to HNOGEOS-Chem Calculation of Contribution of Lightning to HNO33
HNO3 from Lightning Fraction from Lightning
Focus on 200-350 hPa
HNO3 With Lightning (6±2 Tg N yr-1)
No Lightning
Fraction of HNO3 from Lightning
Jan
Jul
Annual Mean HNOAnnual Mean HNO33 Over 200-350 hPa at Locations & Over 200-350 hPa at Locations &
Months with > 60% of HNOMonths with > 60% of HNO33 from Lightning from Lightning
Meridional AverageACE (Uses 81% of Tropical Measurements)
GEOS-Chem with Lightning (-12% bias, r=0.75)
GEOS-Chem without Lightning (-80% bias)
HNO3 Mixing Ratio (pptv)
ACE-FTS
GEOS-Chem with Lightning (6±2 Tg N yr-1)
GEOS-Chem without Lightning
HNO3 Retrieval Error ~35 pptv
OMI/MLS Tropospheric Ozone ColumnOMI/MLS Tropospheric Ozone Column
Jan
Jul
Data from Ziemke et al. (2006)
Calculated Monthly Contribution of Lightning to OCalculated Monthly Contribution of Lightning to O33 Column Column
O3 Column from Lightning Column Fraction from Lightning
Annual Mean Tropospheric OAnnual Mean Tropospheric O33 Columns at Locations & Columns at Locations &
Months with > 40% of Column from LightningMonths with > 40% of Column from Lightning
Meridional AverageOMI/MLS (Uses 15% of Tropical Measurements)
GEOS-Chem with Lightning (-1% bias, r=0.85)
GEOS-Chem without Lightning (-45% bias)
Tropospheric O3 (Dobson Units)
OMI/MLS
GEOS-Chem with Lightning (6±2 Tg N yr-1)
GEOS-Chem without Lightning
O3 Retrieval Error < 5 Dobson Units
ConclusionsConclusions
Global lightning NOx source likely between 4 – 8 Tg N / yr
6 Tg N / yr is a best estimate
Further refinement will require
- improved satellite retrieval accuracy (e.g. NO2)
- more observations (e.g. HNO3)
- model development to better represent processes (e.g. lightning NOx representation, vertical transport)
AcknowledgementsAcknowledgements
Supported by NASA’s Radiation Science Program