Friday, November 6, 2009: 9:20 AM
Charolais (Camino Real Hotel)
Airborne particles can potentially affect climate by absorbing or scattering atmospheric radiation. A key variable describing the radiative effects of aerosols is the single scatter albedo, which is the ratio of the scatter coefficient (bscat) and the extinction coefficient (bext). Our group has previously pioneered a novel measurement method termed the albedometer. It employs cavity ring-down spectroscopy (CRDS) to measure aerosol bext and integrating sphere nephelometry to measure bscat on dispersed particles at concentrations typically encountered in the atmosphere. We have recently implemented several modifications to the original instrument which has allowed > 30 fold improvement in instrument response time while not sacrificing sensitivity. Instrument performance has been characterized by combining electrostatic particle sizing, optical measurements, and particle counting. Measured scattering cross sections have been compared with Mie cross-sections for sub-micron particles of ammonium sulfate. These experiments allow direct validation of measurement accuracy while clarifying the effects of nephelometer truncation error.