ABSTRACT:In this work, the diurnal evolution of the radiation balance components over the tropical Atlantic Ocean is described and analysed. The analysis is based on measurements carried out on board a Brazilian Navy ship during the observational campaign of the FluTuA Project ('Fluxos Turbulentos sobre o Atlântico'), from 15 to 23 May 2002. The observations indicated that the albedo responds as expected to atmospheric attenuation effects with a diurnal evolution similar to the Fresnel albedo. In general, the observed longwave radiation values agreed better with the estimated values obtained without longwave reflection. In agreement with the literature, the average surface emissivity was around 0.97. The net radiation, estimated from published equations for albedo, atmospheric transmissivity and surface emissivity, agreed with the observations, indicating that these parameters are representative of the radiometric properties of the air-sea interface in the region between Natal (6°S, 35.2°W) and the São Pedro and São Paulo Archipelago (1°N, 29.3°W).