1. AGU Fall MeetingDecember 4, 2005 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

2. AGU Fall MeetingDecember 4, 2005 Major Source of Retrieval Uncertainty Ground surface Aerosol Layer 1 Aerosol Layer 2 Light reaching the detector Photon path length is enhanced through multiple scattering by aerosols Incident light

3. AGU Fall MeetingDecember 4, 2005 Global Aerosol Climatology Courtesy: Kahn et al, 2001

4. AGU Fall MeetingDecember 4, 2005 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 => Mie code (de Rooij and van der Stap, 1984) Mineral dust (accumulated/coarse): mixture of oblate and prolate spheroids => T-matrix code (Mishchenko and Travis, 1998) Lognormal distribution Polarization fully considered

5. AGU Fall MeetingDecember 4, 2005 Scattering Matrix (755 nm)

6. AGU Fall MeetingDecember 4, 2005 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: O 2 A band: 17000, CO 2 bands: 20000)

7. AGU Fall MeetingDecember 4, 2005 Weighting Functions (O 2 A Band)

8. AGU Fall MeetingDecember 4, 2005 Weighting Functions (Weak CO 2 Band)

9. AGU Fall MeetingDecember 4, 2005 Weighting Functions (Strong CO 2 Band)

10. AGU Fall MeetingDecember 4, 2005 Retrieval Groups: Single Scattering Albedo

11. AGU Fall MeetingDecember 4, 2005 Retrieval Groups: Normalized Extinction Coefficient

12. AGU Fall MeetingDecember 4, 2005 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

13. AGU Fall MeetingDecember 4, 2005 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

14. AGU Fall MeetingDecember 4, 2005 Acknowledgments OCO L2 Team (JPL) Matt Christi (CSU) Michael Mishchenko (GISS) Olga Kalashnikova and Ralph Kahn (JPL)

15. AGU Fall MeetingDecember 4, 2005 Related Talks/Posters Charles Miller (A14C-02) Hartmut Boesch (A12D-05) Gretchen Aleks (A33B-0883)

16. AGU Fall MeetingDecember 4, 2005 Need to consider both atmospheric/surface and instrumental polarization Importance of Polarization