Modification of Urban Surface Reflection Models with MODIS-AERONET Observations and Validation with High Resolution LANDSAT and HYPERION Imagery

In this presentation, we demonstrate a need for a regionally based surface model based on significant overestimation in the AOD retrieval from MODIS using the current C005 algorithm with respect to AERONET. This is due to the fact that the globally based surface model cannot retrieve the high VIS-SWIR surface reflectance ratio observed when regionally processing urban areas. The resultant surface ratios for urban pixels were found to be significantly higher than those predicted by C005 results with the new surface reflectance ratio (660nm/2160nm) ~ 0.71 while the C005 ratio lies between 0.48 and 0.54. This enhanced ratio was also found to be in good agreement with surface reflectance ratio from complementary studies using Hyperion and Landsat ETM. In addition, we note that the C005 parameterization for the surface reflectance rations with MVI must be substantially modified to account for our regional retrievals as we found the surface reflection ratio to change in the opposite direction with changing MVI compared to the assumed behavior for Collection 5. This model is also shown to be more representative of other urban scenes such as Mexico City.