An algorithm for retrieving black carbon optical parameters from thermal-optical (OC/EC) instruments

Abstract. Through absorption of sun light atmospheric black carbon (BC) is expected to influence regional/global climate by warming the atmosphere and dimming the surface. To evaluate the impact of these effects it is of interest to examine both the radiative properties of BC and the concentrations in air. Building on recent developments we present a novel application for combining these two aspects using the common thermal-optical (OC/EC) instrument. By correlating the OC/EC laser transmission with the FID-carbon detection non-carbon contributions to the light attenuation are detected. Such analysis allows the calculation of mass absorption cross-sections (MACs) for BC, corrected for certain in-organic components. This approach has been applied to data from two SS Asian and two SNS European sites, including a time series analysis for one of the SNS European sites. Taken together this study demonstrates broad applicability for this method while providing new insights into the optical properties of BC.