AIRBORNE ALBEDO MEASUREMENTS OVER THE ROSS SEA, OCTOBER-NOVEMBER 1962

Abstract

During October and November 1962, ten flights were made over the Ross Sea to the north and east of McMurdo, Antarctica, in a Navy C-54Q aircraft fitted with up- and down-facing Epplay pyranometers and with a camera for taking overlapping photographs of the terrain below. From a flight level of 7,500 ft. albedos of the underlying ice types were obtained for various elevations of the sun above the horizon. A few measurements were made from altitudes lower than 7,500 ft. to determine the change of albedo in the vertical. Measurements were made during both clear and cloudy weather, but only those in clear weather or under a uniform overcast are considered reliable. The albedo of old and new winter ice exhibited very little change with elevation of the sun between 10° and 30° above the horizon, the values ranging from 60 to 70 percent but chiefly grouping around 65 percent. Values over young ice ranged from 10 to 25 percent. An albedo of 72 percent was obtained over the Ross Ice Shelf with the sun at 30° above the horizon, and a value of 5 percent was obtained over open ocean with the sun above 40°. Albedos over winter ice and over young ice computed from RG-8 (red) filter data were approximately half those obtained with WG-7 (clear) filter data. From the measurements at intermediate altitudes albedos over pack ice measured with WG-7 filters showed a decrease of about 1.4 percent per 1,000-ft. increase in flight altitude, and albedos over winter ice measured with RG-8 filters showed a decrease of about 5 percent. per 1,000-ft. increase in flight altitude.