Exploring the Potential of Polarimetric Measurements in Studies of Light Absorbing Urban Aerosols

One of the largest uncertainties in climatic studies is the impact of tropospheric aerosols. In particular, the sign of radiative forcing is largely controlled by small variations in the amount and properties of light absorbing aerosols such as black carbon and dust. However, measurements of microphysical and radiative properties of these aerosols have been proven difficult. This study examines the potential of polarimetric measurements to aid in characterizing light absorbing aerosols focusing on the urban environment. A forward radiative transfer model with polarization has been developed which accounts for multiple scattering and light absorption by aerosol particles. The model is used to perform an in depth study to explore the extent to which the degree of linear polarization is sensitive to the microphysical properties of atmospheric aerosols and their vertical distributions. The modeling results are also used to interpret data collected in the Atlanta Metropolitan Area using a CIMEL-318 with a polarimetric channel at 870 nm as well as several other radiation and in-situ optical instruments in conjunction with satellite observations.