Surface temperature and albedo relationships in Senegal derived from NOAA-7 satellite data

Abstract

Ground temperature and albedo values were studied in a semiarid, sub-Saharan region of Africa, Senegal, for various days in the period of September 1981 to October 1982. The albedo and ground temperature were found to be positively correlated; i.e., regions of high albedo were regions of high ground temperature, and regions of low albedo were regions of low ground temperature. Highest values of ground temperature and albedo were found in a region characterized by sparse vegetation and in the dry season. Lowest values of ground temperature and albedo were found in regions characterized by dense vegetation and in the wet season. These results suggest that regions of high albedo in the sub-Saharan region of west Africa are regions of high ground temperature. Mechanisms for increasing the ground temperature under high albedo conditions are discussed. The increased ground temperature will increase the long wave radiation emitted to the atmosphere and the sensible heat flux at the surface. Therefore, there can be a net heat gain in the local atmosphere which will result in a general rising motion. These results are in contrast to those proposed by Charney (1975), who suggested that an increased albedo in semidesert regions will cause a net radiation loss, contributing to net cooling, sinking, and drying of the air aloft.