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Global Climatology of Aerosol Optical Depth. Aaron van Donkelaar, Randall V. Martin: Dalhousie University Ralph Kahn, Robert Levy: NASA Goddard CAFC Meeting 1 February 2010. Average Aerosol Optical Depth ( τ ). Mean τ 2001-2006 at 0.1 º x 0.1 º. MODIS τ 1-2 days for global coverage
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Global Climatology of Aerosol Optical Depth Aaron van Donkelaar, Randall V. Martin: Dalhousie University Ralph Kahn, Robert Levy: NASA Goddard CAFC Meeting 1 February 2010
Average Aerosol Optical Depth (τ) Mean τ2001-2006 at 0.1º x 0.1º • MODIS τ • 1-2 days for global coverage • Requires assumptions about surface reflectivity MODIS • MISR τ • 6-9 days for global coverage • Simultaneous surface reflectance and aerosol retrieval MISR 0 0.1 0.2 0.3 τ [unitless]
Exclude Retrievals Where Bias > 0.1 or 20% July MODIS MISR 9 surface types, defined by monthly mean surface albedo ratios, evaluation against AERONET AOD
Ground-Based PM2.5 Data Useful for Indirect AOD Validation Annual Mean PM2.5 (2001-2006) PM2.5 [μg/m3]
Combining MODIS & MISR Improves Agreement 0.3 0.25 0.2 0.15 0.1 0.05 0 τ[unitless] Combined MODIS/MISR r = 0.63 (vs. in-situ PM2.5) MODIS r = 0.40 (vs. in-situ PM2.5) MISR r = 0.54 (vs. in-situ PM2.5) r=0.45 for a simple average
Mean AOD (2001-2006) from MODIS and MISR Spatial comparison vs AERONET coincident: r=0.97, slope=1.02, 226 sites non-coincident: r=0.75, slope=0.91, 258 sites
