| Description: | Miriam Arak Freedman, CIRES, University of Colorado, "Model Tropospheric Aerosols: Optical Properties and Internal Structure" Abstract The direct and indirect effects of aerosols on climate are currently the largest uncertainties in modeling climate. To better understand the aerosol direct effect, we have investigated the optical properties of model tropospheric aerosols composed of binary mixtures of dicarboxylic acids and ammonium sulfate. Specifically, we have used the new and sensitive technique of cavity ring-down aerosol extinction spectroscopy to retrieve effective refractive indices for aerosol particles. We find that the experimental refractive indices do not agree with volume-weighted average refractive indices, which are commonly used in models. The maximum increase in scattering seen experimentally corresponds to a 40% change in radiative forcing compared with the volume-weighted average refractive indices. Our results suggest that the aerosol particles have complex internal structures. As a consequence, I will discuss the use of atomic force and Raman microscopies for investigating the internal structures of aerosols composed of organic compounds mixed with ammonium sulfate. If time permits, I will also show our preliminary results for the optical properties of aerosol particles with core-shell geometries and angle-resolved scattering from aerosols using a polar nephelometer. |
| Location: | HGS 101 |
| Date: | Friday, December 4, 2009 |
| Time: | 1:30pm-2:30pm CST |
| Duration: | 1 hour |
| Priority: | 5-Medium |
| Access: | Public |
| Category: | Seminar* |
| Created by: | margarita o'connell |
| Updated: | Friday, November 20, 2009 10:48am CST |
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