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