Synthesis of information on aerosol optical properties

In a previous study (Liu et al., 2005) obtained are global scale estimates of aerosol optical depth at 0.55 mm based on spatial and temporal variation patterns from models and satellite observations, regulated by the Aerosol Robotic Network (AERONET) measurements. In this study an approach is developed to obtain information on global distribution of the single scattering albedo (w0), the asymmetry parameter (g), and the normalized extinction coefficient over shortwave (SW) spectrum. Since space observations of w0 are in early stages of development and none are available for g, first an approach was developed to infer them from relevant information from the Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model, Moderate Resolution Imaging Spectroradiometer (MODIS) and AERONET retrievals. The single scattering albedo is generated by extending GOCART w0 at 0.55 mm to the entire SW spectrum using spectral dependence derived from AERONET retrievals. The asymmetry parameter over the solar spectrum is derived from the MODIS A ˚ ngström wavelength exponent, utilizing a relationship based on AERONET almucantar observations. The normalized extinction coefficient is estimated from the MODIS A ˚ ngström wavelength exponent. The methodology was implemented as a ‘‘proof of concept’’ with one year of data. The approach described here is a step in preparedness for utilizing information from new observing systems (e.g., MISR, A-Train constellation) when available. The impact of the newly derived information on the quality of satellite based estimates of surface radiative fluxes was evaluated and is presented by Liu and Pinker (2008).