Polarimetric Remote Sensing of Clouds, Aerosols, and Surface Properties

It is roughly a hundred years ago that the first extremely accurate polarimetric observations of Venus were made by astronomers and another fifty years before the particle scattering and radiative transfer modeling tools were developed that allowed for the interpretation of those observations as being caused by sulfuric acid clouds. Dr. Liou was one of the primary developers of those tools in the early 1970s and, in particular, identified the value of geometric ray tracing for calculating the entire phase matrix for single scattering by large particles. He subsequently used the single scattering properties of ice particles calculated using geometric optics in radiative transfer simulations of light scattering by ice clouds in the visible and infrared. Building on these types of modeling tools and techniques, over the last twenty years significant progress has been made in interpreting polarimetric observations of the Earth. These observations can provide detailed aerosol and cloud properties with unprecedented accuracy. Future satellite missions are expected to use these techniques to facilitate a reliable quantification of the aerosol direct and indirect effects on climate, the most uncertain forcings of climate change. In this talk I will discuss the developments in polarimetric remote sensing that have led to the creation of these capabilities.