HR: 1340h
AN: A33C-1417    [Abstracts]
TI: Using dynamic aerosol optical properties from a chemical transport model (CTM) to retrieve aerosol optical depths from MODIS reflectances over land
AU: * Drury, E E
EM: drury@fas.harvard.edu
AF: Harvard University, Pierce Hall, 29 Oxford St., Cambridge, MA 02138, United States
AU: Jacob, D J
EM: djacob@fas.harvard.edu
AF: Harvard University, Pierce Hall, 29 Oxford St., Cambridge, MA 02138, United States
AB: Quantitative evaluation of modeled aerosol fields from global CTMs with aerosol optical depth (AOD) products retrieved from satellite backscattered reflectances can be compromised by inconsistent assumptions of aerosol optical properties and errors in isolating the atmospheric reflectance signal from the surface reflectance noise. We have developed a method for estimating local (1x1.25 degree) 0.47 μm / 2.13 μm and 0.65 μm / 2.13 μm surface reflectance ratios from MODIS top of the atmosphere (TOA) reflectances under conditions where we expect minimal aerosol reflectance. Using these surface reflectance estimates and dynamic aerosol optical properties from the global CTM GEOS-Chem, we model TOA reflectances at 0.47 μm and 0.65 μm for each MODIS scene in the sun / satellite geometry of the instrument using a radiative transfer model. The modeled reflectances are then fit to the MODIS reflectances by iteratively scaling modeled AODs, resulting in a best estimate of AODs for that scene. The MODIS derived AODs are compared with collocated AERONET AODs over the continental US during the summer of 2004. The AODs retrieved using this method show improved comparison with collocated AERONET AODs ( higher correlations, lower RMSE error and lower bias) than the collection 4 or collection 5 MODIS AOD products, particularly at stations located in the Western and Central US. In addition, the joint comparison of collocated AERONET AODs and MODIS reflectances with modeled AODs and reflectances provides insight on the optical properties (aerosol mixing states and hydroscopicity) of modeled aerosols.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 3360 Remote sensing
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting