Investigators from the Remote Sensing Branch of the Naval Oceanographic and Atmospheric Research Laboratory (NOARL) selected images for inclusion in the Polar Gridded AVHRR Brightness Temperatures data set using hard copy prints from the Navy/NOAA Joint Ice Center (now the National Ice Center). The investigators evaluated the images for areal coverage and degree of cloudiness, and compiled the image evaluations in monthly spreadsheets.
For each image, the investigators noted the date, time, and orbit printed on the hard copy. They subjectively rated each image on a scale of one to five for image clarity and extent of sea coverage. For the January through April, they ranked the seas covered by an image collectively. For instance, a pass covering the Beaufort, Chukchi, and East Siberian Seas might have been given a ranking of 3-4 indicating that about 60 percent of the area covered by the image is cloud-free and that the image covers 80 percent of all three seas combined. For later months, the seas were ranked individually. For instance, an image covering the Beaufort and Chukchi Seas might have been ranked 2-5 for the Beaufort and 3-3 for the Chukchi. In this example, the pass covered 100 percent of the Beaufort and 60 percent of the Chukchi with 40 percent of the Beaufort and 60 percent Chukchi being cloud-free.
The cloud ranking, area ranking, and satellite number (NOAA 10 or 11) for each image are indicated on a spreadsheet under the sea or seas covered by the image. An asterisk denotes an image deemed especially good; two asterisks identify an excellent image. Image passes on order from NOAA and being processed at NOARL at the time of publication of Fetterer and Hawkins (1991) are indicated on the spreadsheets in italics.
Because the National Ice Center separates hard copy imagery based on whether an image is best used for their Eastern or Western Arctic Analysis, the spreadsheets were conveniently divided into eastern and western halves. These areas generally correspond to the European and Pacific Lead ARI grid areas, although the Lincoln Sea and central Arctic are bisected by the Arctic Lead ARI grids.
Monthly spreadsheets for 1989 were included in an appendix of Fetterer and Hawkins (1991) and can be used to facilitate selection of additional passes.
Sample Image Evaluation Spreadsheet for July 1989
Fetterer, F.M. and J.D. Hawkins. 1991. An AVHRR data set for the Arctic Leads ARI. Naval Oceanographic and Atmospheric Research Laboratory, Technical Note 118. 61 p.