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Tropospheric NO 2 columns as a Top-down Constraint on NO x Emission Inventories. Randall Martin Dalhousie University Harvard-Smithsonian Center for Astrophysics. With contributions from Lok Lamsal, Neil Moore, Bastien Sauvage: Dalhousie Univeristy Christopher Sioris: Environment Canada

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slide1

Tropospheric NO2 columns as a Top-down Constraint on NOx Emission Inventories

Randall Martin

Dalhousie University

Harvard-Smithsonian Center for Astrophysics

With contributions from

Lok Lamsal, Neil Moore, Bastien Sauvage: Dalhousie Univeristy

Christopher Sioris: Environment Canada

Rob Pinder: US EPA

uncertainty in emissions remains a major weakness in current models
Uncertainty in Emissions Remains a Major Weakness in Current Models

Estimates of Global NOxEmissions (Range) in Tg N yr-1 for 2000

Fossil Fuel 25 (21-28)

Biomass Burning 6 (3-10)Soils 6 (4-17)Lightning 6 (2-8)

retrieve no 2 columns to map surface no x emissions
Retrieve NO2 Columns To Map Surface NOx Emissions

NOx = NO + NO2

Tropospheric NO2 column ~ ENOx

BOUNDARY

LAYER

hv

NO2

NO/NO2 

W ALTITUDE

NO

O3

lifetime <1 day

HNO3

Emission

NITROGEN OXIDES (NOx)

conduct a chemical inversion for nox emissions
Conduct a Chemical Inversion For NOx Emissions

Need Information on NOx Lifetime, NOx to NO2 Column, Transport

A Priori NOx Emissions

SCIAMACHY NO2 Columns

2004-2005

1011 molec N cm-2 s-1

1015 molec N cm-2

GEOS-CHEM model

A posteriori emissions

Top-Down Emissions

local relationship between no x emissions and no 2 columns can assume linearity around a priori
Local Relationship Between NOxEmissions and NO2 ColumnsCan Assume Linearity Around A Priori

January o Nonlinear__Linear

July *Nonlinear--- Linear

Martin et al., JGR, 2006

slide6
Significant Agreement Between A Priori and A PosterioriLargest Discrepancy in Rapidly Developing Regions

(2000)

r2=0.82

Martin et al., JGR, 2006

speciated inventory for soil emissions
Speciated Inventory for Soil emissions

A posteriori 70% larger than a priori!

A priori

A posteriori

r2= 0.62

(±90%)

(±200%)

Largest soil emissions: seasonally dry tropical + fertilized cropland ecosystems

Onset of rainy season: Pulsing of soil NOx

Jaeglé et al., 2005

slide8

Bottom-up Inventoryfor Soil NOx Emissions

Developments of soil temp/soil moisture, pulsing, fertilizer application

Change in NOx Emissions

Soil NOx Emissions

molec cm-2 s-1

Δ molec cm-2 s-1

Global Total = 7 Tg N/yr

Neil Moore

slide9

Top-down Constraint on Biomass Burning NOx Emissions

GOME

GEOS-Chem (top-down)

GEOS-Chem (bottom-up)

DJF

NO2 Column (1015 molec cm-2)

Observed

Improved simulation of lower tropospheric O3 versus aircraft measurements

Pressure (hPa)

Top-down

Bottom-up

Sauvage et al., ACP, 2007

O3 Mixing Ratio (ppbv)

large differences in no 2 columns reduced with revised amf

BIRA/KNMI

Tropospheric NO2 (1015molec/cm2)

BIRA/KNMI +

Dalhousie AMF

Tropospheric NO2 (1015molec/cm2)

Large Differences in NO2 Columns Reduced With Revised AMF

Eastern China

van Noije et al., 2006

Aaron van Donkelaar

seasonal variation in inferred emissions
Seasonal Variation in Inferred Emissions

OMI (standard)

OMI (NRT)

A priori (NEI2002)

OMI (standard)

OMI (NRT)

A priori (EMEP2003)

March 2006 – Feb 2007

Lok Lamsal

slide13
Ongoing Work at Higher ResolutionAccurate Representation of the Free Troposphere Remains a Challenge

SCIAMACHY

CMAQ (<2km) + GEOS-Chem (>2km)

CMAQ

June - August 2004

Rob Pinder

slide14

Air Mass Factor Calculation in NO2 Retrieval Needs External Info on Shape of Vertical Profile Increased Lightning NOx Emissions Improves GEOS-CHEM Simulation of Midlatitude NO2 ProfilesRemaining Discrepancy: Profile of Emissions

In Situ

0.4 Tg N yr-1

1.6 Tg N yr-1

Midlatitude lightning Mean Bias in AMF:

0.4 Tg N yr-1 12% 9% 3%

1.6 Tg N yr-1 1% 5% 3%

Martin et al., JGR, 2006

slide15

Enhanced Midlatitude Lightning Reduces Discrepancy with SCIAMACHY over North AtlanticRemaining Discrepancy:Profile of NOx Emissions (lifetime)

SCIAMACHY NO2 (1015 molec cm-2)

GEOS-Chem NO2 (1015 molec cm-2)

1.6 Tg N in Midlat

GEOS-Chem NO2 (1015 molec cm-2)

0.4 Tg N in Midlat

May-Oct 2004

Martin et al., JGR, 2006

global lightning nox source remains poorly constrained
Global Lightning NOx Source Remains Poorly Constrained

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

Global rate 44±5 flash/sec [Christian et al. 2003]

DJF

30 – 500moles NO per flash

JJA

Flashes km-2 min-1

current estimate of annual global nox sources as used in geos chem
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

tropospheric no 2 columns retrieved from sciamachy
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)

simplified chemistry of nitrogen oxides exploit longer lifetimes in upper troposphere
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)

strategy
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

simulated monthly contribution of lightning soils and biomass burning to no 2 column
Simulated Monthly Contribution of Lightning, Soils, and Biomass Burning to NO2 Column

Martin et al., 2007

annual mean no 2 column at locations months with 60 from lightning 25 from surface sources
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

Martin et al., 2007

Tropospheric NO2 (1014 molec cm-2)

annual mean hno 3 over 200 350 hpa at locations months with 60 of hno 3 from lightning
Annual Mean HNO3 Over 200-350 hPa at Locations & Months with > 60% of HNO3 from Lightning

Annual Mean Tropospheric O3 Columns at Locations & Months with > 40% of Column from Lightning

Meridional Average

Meridional Average

GEOS-Chem with Lightning (6±2 Tg N yr-1)

GEOS-Chem with Lightning (6±2 Tg N yr-1)

ACE-FTS

OMI/MLS

GEOS-Chem without Lightning

GEOS-Chem without Lightning

HNO3 Retrieval Error ~35 pptv

O3 Retrieval Error < 5 Dobson Units

Martin et al., 2007

slide24

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

Ozone Production Efficiency from lightning = 3 times that of each surface source

Sauvage et al., JGR, 2007

objectives for tropospheric no 2 retrievals
Objectives for Tropospheric NO2 Retrievals

Accuracy of 1x1014 molec cm-2

Resolve seasonal variation over northern midlatitudes

Challenges for Models

Accurate representation of

  • tropospheric NO2 vertical profile
  • NO2 columns / NOx emissions

Acknowledgements

Supported by NASA and NSERC

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