Characterization Of The Global Angstrom Exponent And Aerosol Optical Depth From MISR Observations And IMPACT Model Predictions

Recent progress has been made in characterizing global distribution of aerosol properties from observations and global models. MISR (Multiangle Imaging SpectroRadiometer on EOS Terra) retrievals can contribute to the study of global aerosol characterization by providing, through multi-angular geometry, information about aerosol properties such as optical depth (AOT), single scattering albedo (SSA), angstrom exponent, fraction of coarse to medium-mode aerosols and fraction of spherical to non-spherical particles for quantitative testing of the modeled aerosol transport and deposition. The IMPACT Model (Integrated Massively Parallel Atmospheric Chemical Transport model) simulates trace gases and aerosols comprehensively throughout the troposphere and stratosphere. We seek to verify IMPACT predictions with MISR observations. The Angstrom exponent is a powerful indicator of aerosol size distributions. We explore the global spatial and temporal patterns of MISR observations, with a focus on seasonal, regional and land-ocean differences. The IMPACT model is used to make predictions of the monthly-mean Angstrom exponent at wavelengths corresponding to MISR measurements. We will present an analysis of MISR Level 3 monthly-averaged aerosol optical depth products (0.5 by 0.5 degree grid) in relation to the temporal and spatial monthly-mean global aerosol distribution and aerosol source activity. AERONET data is used to constrain aerosol type and assess the difference between column integrated properties and ground-based properties. In addition, as a component of validating the microphysical representation of processes in IMPACT, we will present a study of the IMPACT-predicted hydroscopic growth of aerosol near land/water boundary in correlation to cases of MISR-observed decrease in the Angstrom exponent values over the ocean compared to those over the land.