AGU Fall MeetingDecember 4, 2005

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Vijay Natraj (California Institute of
Technology) Hartmut Bösch (Jet Propulsion
Laboratory)Yuk Yung (California Institute of
Technology)
Quantifying Aerosol Types and Their Impact on
Trace Gas Retrievals From Satellite Measurements
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Major Source of Retrieval Uncertainty
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Global Aerosol Climatology
Courtesy Kahn et al, 2001
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Aerosol Optical Properties

• Each mixing group is a combination of 4 different
  aerosol components from a basic set of 7 (Kahn et
  al., 2001).
• Sulfate (land/water), seasalt, carbonaceous,
  black carbon spherical gt Mie code (de Rooij and
  van der Stap, 1984)
• Mineral dust (accumulated/coarse) mixture of
  oblate and prolate spheroids gt T-matrix code
  (Mishchenko and Travis, 1998)
• Lognormal distribution
• Polarization fully considered

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Scattering Matrix (755 nm)
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Forward Model Details

• Park Falls, Wisconsin, July (SZA 31 degrees)
• Exponential drop-off in aerosol extinction (scale
  height 1 km, optical depth 0.1)
• OCO spectral regions
• Forward model RADIANT (Christi, CSU) single
  scattering approximation for polarization
• Lorentzian instrument lineshape function
  (resolving powers O2 A band 17000, CO2 bands
  20000)

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Weighting Functions (O2 A Band)
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Weighting Functions (Weak CO2 Band)
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Weighting Functions (Strong CO2 Band)
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Retrieval Groups Single Scattering Albedo
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Retrieval Groups Normalized Extinction
Coefficient
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Sensitivity Tests

• Measurement error 0.43 ppm
• Smoothing error 0.29 ppm
• Error due to incorrect assumption of aerosol type
  within retrieval group
• Group 1 0.27 ppm
• Group 2 0.02 ppm
• Group 3 0.03 ppm

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Conclusions

• Aerosol retrieval groups determined from basic
  aerosol mixing groups
• Choosing incorrect mixing group within retrieval
  group leads to small errors
• Need to test more scattering geometries to
  validate retrieval types
• More realistic aerosol profiles need to be
  included

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Acknowledgments

• OCO L2 Team (JPL)
• Matt Christi (CSU)
• Michael Mishchenko (GISS)
• Olga Kalashnikova and Ralph Kahn (JPL)

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Related Talks/Posters

• Charles Miller (A14C-02)
• Hartmut Boesch (A12D-05)
• Gretchen Aleks (A33B-0883)

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Importance of Polarization

• Need to consider both atmospheric/surface and
  instrumental polarization