STUDY OF A CONTINENTAL SURFACE ALBEDO ON THE BASIS OF FLIGHT MEASUREMENTS AND STRUCTURE OF THE EARTH'S SURFACE COVER OVER NORTH AMERICA*

Abstract

A series of 12 monthly flights along a fixed path in Wisconsin and a series of 4 long-range flights over extensive areas of the United States and Canada were performed during 1963 to measure systematically the surface albedo over various types of the earth's surface, using an instrumented light airplane operating at a low level. An approximate total of 24,000 mi. was flown and roughly 210,000 sets of the measurements were processed for this study. Techniques of measurement and data treatment are discussed. It is shown, and discussed in detail, that the regional differences and seasonal variations of the surface albedo due to thc structure and state of the earth's surface cover are significant. The snow cover is the most important modification of the earth's surface, giving a significantly higher albedo. A quantitative relationship between the increase of surface albedo and snow cover is examined. The surface albedo measured during the flights over typical surface covers over North America, including cities, is presented. The surface covers and their textures over the North American Continent were studied mainly in terms of land use, vegetation type and phenology, soil type, and ground snow cover. The surface albedo values were estimated for various regions of the continent from the flight measurement data, considering the similarity and differences in surface structure among the regions. The resulting seasonal albedo maps of North America are presented and discussed, along with the seasonal variation of the meridional profile of thc continental surface albedo.