Atmospheric aerosol optical property retrieval with scanning polarimeters Kirk D. Knobelspiesse In the last decade, climate models have become increasingly accurate. Simulation of the atmospheric aerosol component of climate models, however, remains highly uncertain. This is largely due to the difficulty of consistent observation of all the aerosol optical parameters required for climate modeling. This, in turn, is primarily because the retrieval of these parameters is often underdetermined, and because the aerosol optical signal is difficult to separate from other signals, such as surface reflection. However, a new class of instruments, called scanning polarimeters, have the potential to improve aerosol optical property retrieval. These instruments use multiple angles, spectral bands, and polarization states to provide measurements with maximized information content that can differentiate aerosols from other scatterers. This research is an investigation of the aerosol retrieving potential of scanning polarimeters, using data collected by the Research Scanning Polarimeter (RSP). The RSP is the airborne prototype of the Aerosol Polarimetry Sensor (APS), soon to be launched into orbit as part of the NASA Glory orbital mission. Field campaign data have already been used to verify the capability of RSP (and APS) to retrieve aerosol properties in cloudless areas over the ocean and land. Here I have continued that work, and investigated the potential for aerosol property retrieval in more complicated scenes, such as aerosols lofted above clouds or extremely large aerosol loads near forest fires. As part of this, I constructed an automated aerosol and cloud retrieval technique that combines a first-principles based atmospheric radiative transfer model with the Levenberg-Marquardt nonlinear optimization approach. This method retrieves both optical parameters and their uncertainties, providing an assessment of optimization success. The software is very flexible, and was also used to determine the sensitivity of the RSP measurements to various parameters that determine atmospheric radiative transfer. These studies will guide both operational APS algorithms and the design of future aerosol remote sensing instruments.