AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Infrared Extinction and Visible Light Scattering Properties of Diatomaceous Earth Aerosol
JENNIFER ALEXANDER, Olga Laskina, Vicki Grassian, Mark Young, Paul Kleiber, University of Iowa
Abstract Number: 277 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Northern Africa is known to be one of the largest sources of atmospheric mineral dust aerosol, especially the Bodélé Depression, located in northern Chad. This atmospheric dust affects the earth’s radiation balance and climate by scattering and absorbing the incoming visible solar radiation and outgoing IR terrestrial radiation. In order to accurately model these radiative transfer effects, dust optical properties must first be known. However, mineral dust optical properties are dependent on particle shape, which is typically nonspherical and can be highly complex. In this work, IR extinction and visible phase function and linear polarization profiles for diatomaceous earth aerosol, a major mineral component of the dust from the Bodélé Depression, are measured and modeled using T-matrix theory based simulations. The particle shape distribution is determined by spectral fitting of experimental infrared (IR) extinction spectral line profile with T-matrix simulations for diatomaceous earth dust. It is found that a particle shape model that peaks toward both extreme rod-like and disk-like shapes results in the best fits to the IR spectral data. SEM images support the extreme particle shape found from spectral fitting. This particle shape model is then used as a basis for modeling the visible light scattering properties, showing a significant improvement over Mie theory based simulations.