Development of a Near-UV Aerosol Albedometer

It is well established that atmospheric particulates, both natural and anthropogenic, directly alter earth's radiative balance by scattering and absorbing solar radiation. The exact magnitude aerosol's direct radiative effect nonetheless remains somewhat uncertain. While research on techniques to characterize aerosols in the visible and near infrared has been ongoing, there has been less attention paid to direct optical characterization of aerosols in the near-ultraviolet (UV) part of the spectrum. This effort will focus on development of an instrument to measure the aerosol scattering coefficient, extinction coefficient, and associated single-scatter albedo at UV wavelengths. This instrument will make use of methodology previously developed by the researchers in which aerosol scattering and extinction coefficients are measured simultaneously on the same aerosol sample dispersed within an integrating sphere. Extinction will be measured using the "cavity ring-down" technique while scattering measurements would be made by collecting light scattered from the probe beam with the integrating sphere. The three-step project plan is to construct the instrument, optimize and characterize its performance in a laboratory setting, and then perform ambient monitoring of aerosol optical properties. The intellectual merit of the research comes through development of provision of key measurements to help to close a major gap in current ability for direct optical characterization of aerosols in the near UV. Broader impacts include increased understanding of aerosol forcing relevant to climate research. Educational and broadening participation aspects will be emphasized via support for two female graduate students and several undergraduates. Public outreach will include a laboratory open-house during periods with many visitors on campus (such as weekend sporting events) to allow the general public an opportunity to see how human activities such as outdoor cooking can alter atmospheric composition.