The University of Wisconsin Space Science and Engineering Center Scanning High-resolution Interferometer Sounder (UW/SSEC S-HIS) is an aircraft-based high spectral resolution infrared spectro-radiometer that has flown on high altitude research aircraft during numerous field experiments. This paper presents a physical retrieval algorithm that was designed specifically for use with the S-HIS instrument. The algorithm uses a Maximum A Posteriori (MAP) approach to the inverse problem, which has an advantage over statistical regression in that it provides error characteristics and an explicit measure of convergence. This methodology requires a priori knowledge of the solution space, and as such, emphasis has been placed on understanding and developing appropriate experiment-specific climatologies. Examples will be presented which illustrate the effect of the a priori climatology (specifically radiosonde vs. NWP climatologies) on the retrieved temperature and moisture profile. We present case studies showing temperature and moisture retrievals from the S-HIS for several recent field campaigns, including CR-AVE (Costa Rica Aura Validation Experiment), JAIVEx (the Joint Airborne IASI Validation Experiment), and TC4 (Tropical Composition, Cloud and Climate Coupling experiment). Comparisons will be made with other field experiment data such as dropsondes, satellite retrievals (Atmospheric Infrared Sounder or AIRS), and several types of radiosondes, in order to provide preliminary validation for the S-HIS retrievals.