Observations and Interpretation of Aerosol Optical Properties from field Measurements: From the Arctic (ICEALOT) to California (CalNex)

“The project has two primary goals associated with the characterization and quantification of light absorption by atmospheric aerosols: 1) analysis of data collected as part of the 2008 ICEALOT campaign and 2) preparation for and participation in the 2010 CalNex campaign. The proposed analysis and measurements will help to advance understanding of the influence of atmospheric aerosols on the Earth�??s climate. Additional goals are to: 1) characterize how well inputs of absorbing carbon to the Arctic are understood, 2) develop a comprehensive summary of the aerosol physicochemical and optical properties, 3) examine to what extent aerosol light absorption measurements correlate with the observation of non-hygroscopic aerosol �??cores�?� and 4) determine how well different light absorption techniques compare when making measurements in a �??clean�?� environment, such as the Arctic. In addition to the analysis of ICEALOT data, the PAS and CRDAES will be deployed onboard the NOAA R/V Ronald H. Brown as part of the 2010 CalNex campaign. The combination of these instruments allows for direct measurement of the particle single scatter albedo. A novel modification of the instruments to be deployed will be the addition of an upstream thermodenuder to selectively remove semi-volatile material from the aerosol prior to the light absorption and extinction measurements. This will allow for quantitative estimates of the contribution of absorption �??enhancements,�?� due to the presence of non-absorbing coatings, to the total light absorption. The ability to use the observed optical properties of the denuded aerosol, specifically the single scatter albedo, to characterize and possibly quantify source contributions will also be examined. Additionally, light extinction measurements will be made on both dry aerosol and aerosol at elevated relative humidity to determine how water uptake affects aerosol light extinction (i.e. measure fext(RH)). Knowledge of both the SSA and fext(RH) is important for quantifying the direct climate impacts of aerosols. Finally, the fast time response of the PAS and CRD-AES will be exploited in order to provide new information on emissions of light absorbing carbon from shipping vessels.”