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Retrieval of Aerosol Absorption and Direct Radiative Forcing over Land

Retrieval of Aerosol Absorption and Direct Radiative Forcing over Land. J. Vanderlei Martins 1,2 , Yoram Kaufman 2 1- University of Maryland Baltimore County – JCET 2 – NASA GSFC. Aerosol Absorption is one of the main uncertainties in Aerosol Direct Forcing

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Retrieval of Aerosol Absorption and Direct Radiative Forcing over Land

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  1. Retrieval of Aerosol Absorption and Direct Radiative Forcing over Land J. Vanderlei Martins1,2, Yoram Kaufman2 1- University of Maryland Baltimore County – JCET 2 – NASA GSFC • Aerosol Absorption is one of the main uncertainties in Aerosol Direct Forcing • Looking for simple approaches to measure aerosol absorption and its effects • The Critical Albedo methodology provide a simple and accurate interpretation of the DRF in the top of the atmosphere • Proposal to NASA NRA: Determination of aerosol absorption and direct radiative forcing using MODIS – Retrospective data set analysis and semi-operational algorithm implementation

  2. AEROSOL DIRECT RADIATIVE FORCING Albedo on TOA o = 0,85, biomass burning aerosol,  = 0,55 m, several AOTs ATOA < ASUP Warming ATOA = ASUP Balance Albedo TOA Acrit t= 3 t=0.2 ATOA > ASUP Cooling Definition of Critical Albedo

  3. Albedo TOA Warming More sensitivity to absorption Cooling AEROSOL DIRECT RADIATIVE FORCING Albedo on TOA o = 0,85, biomass burning aerosol,  = 0,55 m, several AOTs ATOA < ASUP Warming ATOA = ASUP Balance t= 3 t=0.2 ATOA > ASUP Cooling

  4. Albedo TOA Warming More sensitivity to absorption Cooling AEROSOL DIRECT RADIATIVE FORCING Albedo on TOA o = 0,85, biomass burning aerosol,  = 0,55 m, several AOTs Rparticles << RSUP Surface Darkening or Warming Rparticles = RSUP Balance between Absorption and Scattering t= 3 t=0.2 Rparticles > RSUP Surface Brightening or Cooling

  5. Formulation of the Critical Albedo Methodology Dark Surfaces: ATOA = Ao+FdTuASURF Albedo TOA Warming More sensitivity to absorption Cooling

  6. Formulation of the Critical Albedo Methodology Dark Surfaces: ATOA = Ao+FdTuASURF Albedo TOA Warming More sensitivity to absorption Cooling

  7. Extension over Bright Surfaces Ao and Acrit are the essential parameters for the radiative transfer equation

  8. Extension over Bright Surfaces Ao and Acrit are the essential parameters for the radiative transfer equation Acrit wo=0.85 wo=1.0

  9. ATOA and DRFTOA are determined by 2 basic parameters: Ao and Acrit (plus Asurf) • How to determine Ao and Acrit???? • Ao: • MODIS Aerosol Product – MOD04 (at 0.47, 0.66 and 0.55) • Aeronet Sunphotometers • Acrit: • Analytically from wo and g (or b) – Aeronet Sunphotometers or other in situ • Experimentally from MODIS scatter plots • Direct in situ measurements (developing)

  10. Formulation of The Critical Albedo in Single Scattering Approximation: The critical albedo is an intensive property of the aerosol particles. It combines single scattering albedo and phase function in a single parameter capable of describing the direct radiative forcing of the aerosols when compared to the surface albedo. In single scattering approximation, for low optical thickness, and a << 1, the critical albedo can be writen as: wb 2(wb+1-w) Better analytical expression can also be written as well as results can be obtained by accurate radiative transfer codes. Acrit =

  11. Experimental Measurements of Acrit

  12. wob 2(wob+1-wo) Acrit = Warming Aerosol Critical Albedo Albedo Cooling Cerrado Forest

  13. Acrit from Aeronet Sunphotomers wo, p(q)

  14. Smoke From Biomass Burning in Brazil

  15. Smoke From Biomass Burning in Brazil

  16. Operational Cloud Mask

  17. New Spatial Variability Mask over Land

  18. Images 16 days apart, after applying cloud mask

  19. Projection over the same grid – about 2km resolution

  20. Projection over the same grid – about 2km resolution Comparison of 10x10km boxes between both images for each wavelength

  21. Comparison of 10x10km boxes between both images for each wavelength

  22. Critical Reflectance for determining aerosol absorption: a version is being tested operationally in MODIS

  23. Operational Modis AOT Product(smoothed) Path Radiance 0.66mm from the 2 days comparison (min=-0.05,max=0.15)

  24. Path Radiance 0.66mm from the 2 days comparison (min=-0.05,max=0.15) Critical Albedo MODIS 0.66mm (min=-0.5, max=0.5)

  25. -Heating index 0.86 (-0.5,+0.5), for Acrit=0.25 Albedo 0.86 (0,+0.5) Lat = (0,-20) Lon=( -52,-72) Eric Moody.

  26. -Heating index 0.66 (-1.5,+1.5), for Acrit=0.25 Albedo 0.66 (0,+0.2) Lat = (0,-20) Lon=( -52,-72) Eric Moody

  27. -Heating index 0.66 (-1.5,+0.5), for Acrit=0.25 Albedo 0.66 (0,+0.2) Lat = (0,-20) Lon=( -52,-72) Eric Moody.

  28. AEROSOL DIRECT RADIATIVE FORCING Smoke – Instantaneous Direct Radiative Forcing over Varying Surface Albedo (Cuiaba – Brazil) for t = 1 Rparticles << RSUP Surface Darkening or Warming - 95 W/m2 Rparticles = RSUP Balance between Absorption and Scattering +10 W/m2 DRF Rparticles > RSUP Surface Brightening or Cooling Large contrast in radiative forcing due to the combination of surface and aerosol properties

  29. Spatial Distribution of Instantaneous Smoke Radiative Forcing at TOA (Cuiaba – Brazil, AOT = 1.0) W/m2 -95 -40 +10 12 km • Remote sensing of aerosols: Properties and Effects • Cloud masking Optical Properties • Aerosol radiative forcing Aerosol + Cloud interactions Figure shows the large contrast in radiative forcing due to the combination of surface and aerosol properties What are the Effects of this Variability on the Regional Dynamics???

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