In this project, key questions related to PSC formation and evolution and their representation in global models will be addressed through the following main objectives: identify the key PSC parameters which are required by global models; compare remote and in situ datasets to identify their strengths and limitations; define a methodology to obtain the key PSC properties required by models from the observational datasets; synthesize the new satellite measurements and earlier datasets into a state of the art PSC climatology; and identify remaining open science questions.