A technique has been developed from simultaneous satellite and aircraft data that allows the magnitude and gradient of the earth's surface albedo to be inferred from satellite measurements of the earth-atmosphere system brightness. The technique uses the visible brightness observations from the SMS-1 geosynchronous satellite made during the GARP Atlantic Tropical Experiment (GATE) in 1974. Direct albedo measurements from aircraft verified an albedo range of from 50% over the Sahara Desert to 7% over the wet tropical rainforests. The technique is used to study the changes in the physical characteristics of the surface of northwestern Africa's Sahel region between July and September, 1974. Changes in the gradient of surface albedo and areal extent of various vegetation types are inferred. The albedo values calculated through the application of this technique should be incorporated into the numerical and analytic models of the atmosphere that have recently been used to study local circulation patterns and precipitation trends.