Toward unified satellite climatology of aerosol properties: Direct comparisons of advanced level 2 aerosol products

The development of a unified satellite climatology of aerosol properties requires accurate quantification and deep understanding of the underlying factors contributing to discrepancies between individual satellite products. In this paper we compare the most recent level 2 results obtained for coincident pixels viewed at essentially the same time by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging Spectroradiometer (MISR) instruments flown on the EOS Terra platform. This strategy eliminates potential sampling effects and provides a virtually direct comparison of spatially and temporally collocated MODIS and MISR retrievals. We show that the MODIS and MISR Ångström exponent datasets reveal essentially no correlation. Although the corresponding aerosol optical thickness (AOT) datasets can agree worse than expected over the oceans, still the agreement is often satisfactory. However, the agreement over the land is often poor or even unacceptable. Of the collocated pixels for which there is a MODIS aerosol retrieval, only ∼40% or fewer pixels have a MISR aerosol retrieval, and vice versa. These findings further illustrate the complexity of the problem of aerosol retrievals from satellite observations and indicate that the creation of a meaningful unified MODIS-MISR aerosol climatology will be a nontrivial task.