PNNL

Abstract

Multi-wavelength aerosol extinction, absorption and scattering measurements made at two ground sites during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) are analyzed using a spectral deconvolution method that allows extraction of particle size-related information, including the fraction of extinction produced by the fine mode particles and the effective radius of the fine mode. The spectral deconvolution method is typically applied to analysis of remote sensing measurements. Application to in situ measurements allows for comparison with more direct measurement methods and validation of the retrieval approach. Here, the retrieved fine mode fraction and effective radius generally compare well with other in situ measurements, including size distribution measurements and scattering and absorption measurements made separately for PM1 and PM10, but some limitations are also identified. These results indicate that for campaigns where size, composition, and multi-wavelength optical property measurements are made, comparison of the results can result in closure or can identify unusual circumstances. The comparison here also demonstrates that in situ multi-wavelength optical property measurements can be used to determine information about particle size distributions in situations where direct size distribution measurements are not available.