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Simultaneous Retrieval of Aerosol and Surface Properties from Satellite Data

Development of an algorithm for simultaneous retrieval of aerosol properties and surface conditions using AERONET, MODIS, MISR, and POLDER data. The method reduces assumptions in the retrieval by combining ground-based and satellite observations and considering multiple parameters. Statistical optimization and numerical inversion techniques are employed for accurate results.

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Simultaneous Retrieval of Aerosol and Surface Properties from Satellite Data

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  1. Simultaneous Retrievals of aerosol and surface from a combination of AERONET- MODIS-MISR-POLDER data Algorithm:Oleg Dubovik1, Alexander Sinyuk1, MODIS: Yoram Kaufman1 Eric Vermote2 Jean-Claude Roger2 MISR: John Martonchik3, Ralph Kahn3, Dave Diner3, POLDER: Francois-Marie Breon4, AERONET: Brent Holben1, Ilya Slutsker1 1- NASA/GSFC, Greenbelt, MD, USA 2 - UMD, Greenbelt, MD, USA 3 - NASA/JPL, CA, USA 4 - CEA/DSM/LSCE, France

  2. Retrieval of surface needsatmospheric correction for aerosol effect Retrieval of aerosol reliesonassumption of surface reflectance Idea:Less assumptions are needed in simultaneous retrieval of aerosol and surface from combination of up- and down - looking observations

  3. Retrieval using combinations of up-looking Ground-based and down-looking satellite observations Retrieved: Aerosol Properties: - size distribution - real ref. ind. - imag. ref. ind (AERONET sky channels) • Surface Parameters: • BRDF (MISR, POLDER) • Albedo (MODIS)

  4. AERONET- MISR - POLDER - MODIS data • AERONET Ground-based Sun-sky radiometer: - t(l) ± 0.02 at 6 channels: 0.34, 0.38, 0.44, 0.67, 0.87, 1.02, 1.65mm • I(l,Q) ± 0.05% at 4 channels: 0.38, 0.44, 0.67, 0.87, 1.02, 1.65mm 3° ≤ scattering angles ≤ ~70° • P(l,Q) ± 0.02% at 0.87 • MISR Reflectance at 4 channels: 0.45, 0.55, 0.67, 0.87 mm 9 viewing angles: ±70.5o, ± 60o,± 45.6o, ± 26.1o, 0o • MODIS Reflectance at 7 channels: 0.47, 0.55, 0.66, 0.87,1.2, 1.6, 2.1 • POLDER Reflectance at 7 channels: 0.44, 0.49, 0.56, 0.67,0.76, 0.87, 0.91 13 viewing angles Polarization at: 0.44, 0.67, 0.87

  5. Retrieval scheme: MISR, POLDER MODIS • Forward model: • - Detailed aerosol (same as in AERONET) • Multiple scattering accounts for BRDF • BRDF modeled using parameterized model • (Rahman-Pinty-Verstraete, 1993) Numerical inversion: -Accounting for noise -Solving Ill-posed problem - Setting a priori constraints Observations aerosol particle sizes, complex refractive index, parameters of BRDF (or Lambertian albedo)

  6. Inversion • Statistically Optimized Minimization- • Multi-term LSM Fitting (Dubovik and King 2000; Dubovik 2004) weighting Lagrange parameters • Measurements: • i=1 - optical thickness • i=2 - AERONET radiances • i=3 - stellite radiances • their covariances • (should depend on l and Q) • -lognormal error distributions a priori restrictions on norms of derivatives of: i=4 -size distr. variability; i=5 -n spectral variability; i=6 -k spectral variability; i=7 - surface reflectance spectral variability; consistency Indicator

  7. Questions & Issues: • Retrieved aerosol properties: • are there any improvements compare to conventional AERONET retrieval • Retrieved surface properties: • reliable? • are there any limitations? • what is the difference with conventional atmospheric correction?

  8. August 9, 2003 t(0.44) ~ 0.3 Simultaneous fitting AERONET MODIS

  9. Summer, 2003 MONGU Simultaneous fitting August 9, 2003 t(0.44) ~ 0.3 MISR-MODIS MISR MODIS

  10. Comparisons of Surface Retrievals (with improved vertical profile) Surface Albedo: Surface BRDF:

  11. Effect of Aerosol Vertical Distribution on the Surface Retrievals Assumed Profiles:

  12. Surface Effect on Retrievals of the Refractive Index (low aerosol loading) POLDER: June 24, 2003 t(0.44) ~ 0.26 , SZA=470 MISR: August 9, 2003 t(0.44) ~ 0.3, SZA=400

  13. Surface Effect on the Retrievals of the Size Distribution (low aerosol loading) MISR: August 9, 2003 t(0.44) ~ 0.3, SZA=400 POLDER: June 24, 2003 t(0.44) ~ 0.26 , SZA=470

  14. Surface Effect on the Retrievals at High Aerosol Loading POLDER: August 18, 2003 t(0.44) ~ 0.63, SZA=350

  15. Surface Effect on the Retrievals of Single Scattering Albedo MISR: August 9, 2003 t(0.44) ~ 0.3, SZA=400 POLDER: August 18, 2003 t(0.44) ~ 0.63, SZA=350

  16. Effect of Particle Non-Sphericityon the Retrievals June, 2003 Solar Village, Saudi Arabia

  17. Surface Effect on the Retrievals of Single Scattering Albedo (Almucantar inversion with corrected surface) POLDER: June 7, 2003 t(0.44) ~ 0.67 , SZA=700 POLDER: September 27, 2003 t(0.44) ~ 0.24 , SZA=700

  18. Retrievals for Islands or Costal sites Cape Verde (Island)

  19. Results: • Simultaneous inversion of satellite and AERONET data has been developed • Surface BRDF and Albedo can be retrieved simultaneously with aerosol (low and moderate t,) • Improved retrievals of aerosol: - refractive index and size (low tover vegetation) - wo(l) and size (over bright surface) • The approach is very useful for sites with complex surface structure (Islands, costal) Plans: • Completing analysis • Making operational retrievals • Including Lidar information

  20. Comparisons of MISR and POLDER geometries Mongu, August 7,9 ,10, 2003

  21. Almucantar and principle plane retrievals: Size Distribution POLDER: June 7, 2003 t(0.44) ~ 0.67 , PP: SZA=230; ALM: SZA=700 POLDER: September 27, 2003 t(0.44) ~ 0.24 , PP: SZA=340; ALM: SZA=700

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