Quantitative Interpretation of Satellite and Surface Measurements of Aerosols over North America

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Quantitative Interpretation of Satellite and
Surface Measurements of Aerosols over North
America

• Aaron van Donkelaar
• M.Sc. Defense
• December, 2005

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Aerosols Why do we care?

• Climate Change
• Direct Effect
• Indirect Effect
• Health Effects (PM2.5)
• Lung cancers
• Pulmonary Inflammation
• Visibility

Image from http//cariari.ucr.ac.cr/faccienc/tema
s2/planeta.htm
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Part I Remote Sensing of Ground-Level PM2.5
Column Mass Loading
Ground-Level PM2.5

• ? particle mass density
• r effective radius
• t aerosol optical depth
• Qe Mie extinction efficiency
• z Height of regional air mass
• subscript d denotes dry conditions

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Instrumentation

• MODIS
• Moderate Resolution Imaging Spectroradiometer
• 32 channels (7 used for Aerosol Retrieval) 0.47,
  0.55, 0.67, 0.87, 1.24, 1.64 um
• Approx. daily global coverage
• Requires dark surface for AOD retrieval

• MISR
• Multiangle Imaging Spectroradiometer
• 4 spectral bands at 9 different viewing angles
• 6-9 days for global coverage
• No assumption regarding surface reflectivity

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GEOS-CHEM

• 50 Tracers
• 1º x 1º resolution
• 30 vertical levels (lowest at 10, 50, 100, 200,
  300 m)
• GMAO fields temperature, winds, cloud
  properties, heat flux and precipitation
• sulphate, nitrate, mineral dust, fine/coarse
  seasalt, organic and black carbon

• Aerosol and oxidant simulations coupled through
• formation of sulphate and nitrate
• heterogeneous chemistry
• aerosol effect of photolysis rates
• Seasonal average biomass burning

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Remote vs. Ground PM2.5
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Scatter Plot Comparison/Table Holding Constants
MODIS MISR
standard 0.68 0.54
constant vertical structure (tz/t) 0.29 0.29
constant AOD 0.54 0.38
constant aerosol properties (Qe, r, rd, ?d) 0.73 0.52
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Temporal Correlation
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Global PM2.5
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Part II Organic Aerosol Sources

• Primary Sources
• combustion (biomass/biofuel)
• Secondary Sources
• condensation of gaseous species
• not well understood
• GEOS-CHEM OA Simulation
• Seasonally varying biomass burning inventories
• Inversion removed
• SOA based upon Chung and Seinfeld 2002
• Biogenic emissions from MEGAN inventory
• HxCy (O3, OH, NO3) ? semi-volatile products

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IMPROVE Organic Aerosol
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IMPROVE GEOS-CHEM Organic Aerosol
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Isoprene conversion fits within model biases
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Large effect from non-OA condensation
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Conclusions

• Remote PM2.5
• significant correlation (MODIS R0.68,
  MISR0.54)
• dominant factors include AOD and vertical
  structure
• reveals global regions of high PM2.5
• Sources of Organic Aerosol
• isoprene conversion reduces model bias
• non-OA condensation unclear