The newly available AVHRR (Advanced Very High Resolution Radiometer) Polar Pathfinder (APP) data set provides a tremendous opportunity to examine the spatial and temporal variability of surface, cloud, and radiative characteristics in the data-sparse polar regions. The 20-year APP data set consists of twice-daily composites covering both polar regions at a 5 km pixel size. The standard APP products include radiances, viewing and illumination geometry, three cloud masks, clear sky surface temperature and albedo, and ice motion. We have extended this product suite to include cloud properties and radiation fluxes. The extended products have been validated primarily with data collected during Surface Heat Balance of the Arctic Ocean (SHEBA) field experiment that took place in the western Arctic Ocean from the fall of 1997 through the fall of 1998.

In this study 10 years of APP data, subsampled to a 25 km scale, are used to generate a climatology of cloud amount, optical depth, particle size, temperature, particle phase, surface temperature and albedo, and surface and top-of-atmosphere radiation fluxes. Monthly means of surface and cloud properties are compared to those in the International Satellite Cloud Climatology Project (ISCCP) "D2" cloud product. An analysis of seasonal and interannual variability in these parameters is presented. Semi-variograms are also used to examine the spatial and temporal persistence in the data. Results indicate that downwelling shortwave and longwave fluxes exhibit temporal correlation over about 180 days, but cloud optical depth and cloud fraction show almost no correlation over time. The spatial variance of surface properties is shown to increase much less rapidly than that of cloud properties.