(447f) Detailed Evaluations of Optical Property Models for Mineral Dust Aerosol

Mineral dust is a major component of the total global aerosol load and plays a critical role in establishing the physical and chemical equilibrium of the atmosphere. In particular, mineral dust affects the Earth's radiation balance by direct light absorption and scattering across the spectrum from the IR to the UV. Climate models require detailed information about the aerosol population, such as size, shape and chemical composition, and an accurate treatment of dust optical properties. The aerosol population is often characterized via remote sensing methods which, in turn, rely on optical property models. Thus, deficiencies in the optical property models can compromise the results of global climate models. Our laboratory has developed several unique laboratory capabilities to measure dust optical properties and to explore how chemical processing in the atmosphere alters those properties. We have been particularly interested in particle shape effects and the ramifications for light scattering theories. Our recent work suggests that atmospheric dust particles may have more eccentric shapes than previously thought and that common assumptions about particle shape distributions can lead to errors in remote retrieval algorithms. We will report on our use of correlated IR extinction measurements and angle-resolved light scattering to more accurately incorporate particle shape effects into T-matrix theory treatments. The goal is to establish empirical methodologies for using the correlated data to facilitate more accurate dust retrievals from remote sensing and to improve accuracy in modeling dust radiative transfer effects in climate modeling. We also consider how aerosol properties might change as particles undergo physical and chemical processing typical of atmospheric aging.