The AVHRR Polar Pathfinder (APP) and Extended AVHRR Polar Pathfinder (APP-x) Climate Data Records provide a comprehensive set of variables that can be used to study trends and interactions within the Arctic and Antarctic climate systems. APP is a fundamental Climate Data Record (CDR) that provides channel reflectances and brightness temperatures. APP-x is a thematic CDR that builds on APP to provide information about surface and cloud properties and radiative fluxes. Both data sets provide twice daily observations spanning the period 1982 to present, for both polar regions. The APP and APP-x CDRs are described in detail in:

Key, Jeffrey, et al. 2016. The AVHRR Polar Pathfinder Climate Data Records. Remote Sens. 8(3):167. DOI: http://dx.doi.org/10.3390/rs8030167