Extended AVHRR Polar Pathfinder (APP-x)

The joint National Oceanic and Atmospheric Administration/National Aeronautics and Space Administration (NOAA/NASA) Advanced Very High Resolution Radiometer Polar Pathfinder (APP) project recently produced 30 years of twice- daily, bi-polar surface temperature, surface albedo, and cloud information products. The APP data is being extended to include cloud properties and surface radiative fluxes. The figures below give examples of the product. The extended APP data set covers 1982-2011 at a spatial resolution of 25 km. Validation of the algorithms has been done primarily with data from the Surface Heat Budget of the Arctic (SHEBA) field experiment.

Sea Ice Thickness

Here are a few more examples:

Data Availability

The monthly APP-x data product is available here. Due to the high data volume (60 GB), the twice daily product is only available by special request.


A subset of the APP+ data product for the SHEBA region has been used to calculated the potential bias in radiative fluxes that can occur in climate and sea ice models due to subgrid cell variability of suface and cloud properties. This issue is described in more detail here.

More applications will be posted here as they become available.


This research is being (or was) performed by the following people: Xuanji Wang and Jeff Key.


This research was supported by the National Science Foundation and NOAA.


Wang, X. and J. Key, 2005, Arctic surface, cloud, and radiation properties based on the AVHRR Polar Pathfinder data set. Part I: Spatial and temporal characteristics, J. Climate, 18(14), 2558-2574.

Wang, X. and J. Key, 2005, Arctic surface, cloud, and radiation properties based on the AVHRR Polar Pathfinder data set. Part II: Recent trends, J. Climate, 18(14), 2575-2593.

Wang, X. and J. Key, 2003, Recent trends in Arctic surface, cloud, and radiation properties from space, Science, 299(5613), 1725-1728. (Link to on-line Science paper)

Key, J., 2000. The Cloud and Surface Parameter Retrieval (CASPR) System for Polar AVHRR Data User's Guide. Space Science and Engineering Center, University of Wisconsin, Madison, WI, 62 pp.

Maslanik, J., J. Key, C. Fowler, T. Nyguyen, X. Wang, 2000. Spatial and temporal variability of surface and cloud properties from satellite data during FIRE-ACE. J. Geophys. Res., in press.

Maslanik, J., C. Fowler, T. Scambos, J. Key, and W. Emery, 1997. AVHRR-based polar pathfinder products for modeling applications. Annals Glaciol., 25, 388-392.