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Terra Observations of Tropospheric Terra Observations of Tropospheric

Aerosol and CO from Biomass BurningAerosol and CO from Biomass Burning

David Edwards, Xuexi Tie, Louisa Emmons, and John GilleNational Center for Atmospheric Research, Boulder CO, USA

Allen Chu and Yoram KaufmanNASA Goddard Space Flight Center, Greenbelt MD, USA

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• Approximately half-billion hectares of natural and human-induced biomass burning occurs each year

• In tropical regions, biomass burning for cultivation, deforestation and savanna grazing is a major forcing mechanism for tropospheric photochemistry

• Fires emit large amounts of aerosol, CO, and hydrocarbons which strongly affect tropospheric O3 and the oxidising capacity of the atmosphere

• In addition to a climatic impact that is not well quantified, this also has implications for weather modification and air quality

Biomass Burning: Impacts on Tropospheric Chemistry and Climate

David Edwards, NCAR

Coarse mode

Fine Mode

MODIS Aerosol

(AOD)

Sept. 2000

• MODIS can distinguish between coarse and fine particles using multiple channels from the visible to the near IR

• Course aerosol mode: Mainly dust and sea salt

• Reflects in the VIS & NIR: Appears red in the VIS due to absorption in the blue

• Surface characterization is an issue over land

• Fine aerosol mode: Anthropogenic pollution and biomass burning

• Reflects mainly in the VIS

David Edwards, NCAR

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• Good correlation is obtained between MODIS fine mode AOD & MOPITT CO

• Both CO and fine mode aerosol result from anthropogenic combustion processes: urban pollution, industry, and tropical biomass burning

MODIS Aerosol& MOPITT CO

Fine Mode AOD

CO Column

MODIS

MOPITT

Sept. 2000

David Edwards, NCAR

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• Southern African burning is a maximum in Sept.-Oct.

• Anti-cyclonic winds in southern Africa and the southern Atlantic result in strong re-circulations

• A stable mixing layer over Africa provides containment for several days

• Part of the African plume is advected into the Atlantic

• Periodically, the plume is advected south-east and caught in the westerly flow at higher southern latitudes

• This an important mechanism providing for the long-range export of emissions

• In Brazil, strong convection lifts emissions to the mid troposphere

• The South American plume is advected south-east across the Atlantic

• The Atlantic becomes crossed by plumes moving in opposite directions

South African & South American Plumes

Ten day trajectories starting 9-15-00 using HYSPLIT

David Edwards, NCAR

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Prescribed burn near Kruger National Park, South Africa, September 7, 2000.Photo from the Convair-580 (Flight 1834) during SAFARI 2000 by Peter Hobbs, UWA.

SeaWiFS true-color image acquired over Southern Africa, September 4, 2000. Data acquired by the Satellite Applications Center, Pretoria, South Africa.

David Edwards, NCAR

MODIS Fine Mode AOD MOPITT 700 hPa CO

AOD/CO Ratio

Plume aging can be followed as the AOD/CO ratio falls, indicating persistent CO but reduced aerosol loadings due to the shorter aerosol lifetime

David Edwards, NCAR

100 200 300 400 500day from 1/1/2000

0

10

20

30

40

MOPITT (Night, w/in 100km)MOPITT (Day, w/in 100km)

FTIR

• MOPITT and ground-based FTIR CO total column measurements taken at Lauder, New Zealand.

• The plume from biomass burning causes a peak in the measured CO in the usually clean air over New Zealand

October 1-15, 2001 Providing global context to local measurements: Long-range transport of biomass burning products

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170

0.10 0.50 1.00 1.50 1.75 2.00 2.25 2.50 3.00 3.50 1018 mol/cm2

MOPITT CO total column, Oct. 1-15, 2000

FTIR data: N. Pougatchev, NASA & N. Jones, NIWADavid Edwards, NCAR

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MODIS AOD

Fine Mode

MOPITT CO

Total Column

David Edwards, NCAR

TRMM/VIRS Fire Counts MODIS Fine Mode AOD

GOME NO2 Tropospheric ResidualMOPITT CO Column

Satellite Observations of Biomass Burning and Resultant Plumes: Sept. 2000

Andreas Richter, U. Bremen

David Edwards, NCAR

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• Black carbon from biomass burning strongly absorbs solar radiation and can potentially reduce photolysis rates within biomass burning plumes

• Reduction in photolysis can lead to a compensating offset to the expected increase in O3 production due to the higher concentrations of NOx, CO, and other hydrocarbons

• Heterogeneous reactions on BC particles can also affect O3 concentrations and the uptake coefficient for O3 on BC particles remains uncertain

Effect of Aerosol on Ozone Production

TUV photolysis rate calculation in a BC layer of AOD at 340 nm of 0.5 in the lowest 3km of the atmosphere

J[NO2]

J[O3]

Clear Sky

BC Layer

Clear Sky

BC Layer

David Edwards, NCAR

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• The combination of measurements from the new tropospheric satellite sensors will play an increasingly important role in explaining chemistry and transport processes in the lower atmosphere

• This will be complimentary to continued in-situ measurements and modeling for sensitivity and process studies

• MOPITT CO and MODIS fine/coarse particle measurements can be combined to examine the seasonal variability and transport of aerosols and trace gases in biomass burning plumes

• Provides information about continental export and the impact of intense fire sources on global scale air quality

• Variations in plume relative composition for different burning regimes might potentially provide information about emission factors

• Detailed examination of O3 precursor emissions and transport, and the effect of BC on photolysis and heterogeneous chemistry is still required to quantify the impact on the tropical tropospheric O3 distribution

Summary

David Edwards, NCAR