Analysis of Satellite Observations to Estimate Production of Nitrogen Oxides from Lightning

Randall MartinBastien Sauvage

Ian FolkinsChris Sioris

Chris Boone Peter Bernath

University of Saskatchewan

Jerry Ziemke

Global Lightning NOx Emissions Remain Poorly ConstrainedGlobal Lightning NOx Emissions Remain Poorly Constrained(1–13 Tg N/yr)(1–13 Tg N/yr)

Flashes km-2 min-1

DJF

JJA

10-year Mean Flash Rate from the OTD & LIS Satellite Instruments10-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

Top-down Information from the SCIAMACHY, ACE, Top-down Information from the SCIAMACHY, ACE, OMI, and MLS Satellite InstrumentsOMI, and MLS Satellite Instruments

SCIAMACHY Aug 2002-presentNadir spatial resolution 60x30 km2

Tropospheric NO2 Columns (Martin et al., in press)

ACE-FTS Jan 2004-present Limb Measurements in the Upper TroposphereHigh Resolution FTS (33 species)HNO3 (Bernath et al., 2005; Boone et al., 2005)

OMI & MLS Aug 2004-presentBoth instruments onboard Aura satelliteOMI nadir UV-Vis, 24x13 km2 with daily global coverageMLS thermal emission microwave limb sounder Tropospheric O3 (Ziemke et al., in press)

Current Estimate of Annual Global NOx EmissionsCurrent Estimate of Annual Global NOx Emissions

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%)

Martin et al., in pressTropospheric NO2 (1015 molecules cm-2)

Nov - Apr

May - Oct

NO/NO2

w Altitude

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 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 ModelGEOS-Chem Chemical Transport Model• Assimilated Meteorology (NASA GMAO)

• 2ox2.5o horizontal resolution, 30 vertical layers

• O3-NOx-VOC chemistry

• Lightning: 6 Tg N/yr, Price and Rind (1992), Pickering et al. (1998)

• Aerosols: SO42--NO3

--NH4+-H2O, dust, sea-salt, carbonaceous

Bey et al., 1999 Fiore et al., 2002Martin et al., 2002, 2003Park et al., 2003, 2004

41 tracers ~90 species 300 reactions

Calculated Monthly Contribution of Lightning and Soils to Calculated Monthly Contribution of Lightning and Soils to NONO22 Column Column

Column Fraction from Lightning (6 Tg N / yr)

Column Fraction from Soils (6 Tg N / yr)

UnitlessUnitless

Jan

Jul

Jan

Jul

GEOS-Chem Tropospheric NO2 Column

1015 molec cm-2

Annual Mean Tropospheric NOAnnual Mean Tropospheric NO22 at Locations & Months with at Locations & Months with

>50% of Column from Lightning and <25% from Soils>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 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 200-300 hPa for Jan 2004 – Feb 2006 over 200-300 hPa for Jan 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

Δpptv Unitless

Focus on 200-300 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 200-300 hPa at Locations & Over 200-300 hPa at Locations &

Months with > 60% of HNOMonths with > 60% of HNO33 from Lightning from Lightning

Smoothed Meridional AverageACE (Uses 70% of Tropical Measurements)

GEOS-Chem with Lightning (-1% bias, r=0.74)

GEOS-Chem without Lightning (-79% bias, r=0.15)

HNO3 Mixing Ratio (pptv)

ACE

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

Dobson units Data from Ziemke et al. (in press)

Calculated Monthly Contribution of Lightning to OCalculated Monthly Contribution of Lightning to O33 Column Column

O3 Column from Lightning

Column Fraction from Lightning

ΔDobson Units Unitless

Jan

Jul

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 25% of Tropical Measurements)

GEOS-Chem with Lightning (4% bias, r=0.70)

GEOS-Chem without Lightning (-42% bias, r=0.70)

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 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. NO2)

- more observations (i.e. HNO3)

- model development to better represent processes (i.e. soil NOx, vertical transport, ice uptake of HNO3)

AcknowledgementsAcknowledgements

• National Aeronautics and Space Administration (NASA)

• Natural Sciences and Engineering Research Council of Canada (NSERC)