This data set consists of AVHRR retrievals of surface and cloud properties as well as radiative fluxes during the SHEBA (Surface HEat Budget of the Arctic Ocean) experiment. The data set covers the entire Arctic, twice daily, for 1997 and 1998. A 5 km data set covering the western Arctic is also available.

SHEBA is a multiagency experiment that took place from the fall of 1997 through the fall of 1998. During that period a Canadian icebreaker frozen into an ice floe was used as a base for scientific studies of the ocean, ice, and atmosphere. Research aircraft from the U.S. (NCAR C-130, NASA ER-2, and UW Convair) and Canada (Candian Convair) also took part in the experiment during the spring and summer of 1998.

Cloud and surface properties were estimated from AVHRR data for the SHEBA year. Five kilometer data from the AVHRR Polar Pathfinder project were used in the analyses, subsampled to 25 km. All images are centered on 04:00 (low sun) and 14:00 (high sun) local solar times, though the pixels within any given image may have been acquired 1-3 hours before or after those times. The retrieval algorithms of the Cloud and Surface Parameter Retrieval (CASPR) system were applied. The following parameters are available:
 

Surface and Clouds:

Radiation:

Surface temperature, clear or all-sky Broadband albedo, clear or all-sky Cloud particle effective radius Cloud optical depth Cloud particle phase Surface type mask Cloud top temperature Cloud top pressure Precipitable water

Downwelling shortwave flux at the surface Downwelling longwave flux at the surface Upwelling shortwave flux at the surface Upwelling longwave flux at the surface Downwelling shortwave flux at the top of the atmosphere Upwelling shortwave flux at the top of the atmosphere Upwelling longwave flux at the top of the atmosphere Shortwave cloud forcing at the surface Longwave cloud forcing at the surface

Here are two examples of the data set. The top image shows the all-sky broadband surface albedo over the Arctic for the month of June 1997 at 1400 local solar time. The second image shows the monthly average downwelling longwave flux at the surface for the same month. The images have been remapped to a polar stereographic projection.