An experimental study of the albedo of the sea surface for shortwave solar radiation has been carried out on a fixed platform. Fifteen-minute totals of upward and downward irradiances were recorded continuously for four months over a wide range of atmospheric and sea conditions. The resulting albedo values, the ratio of upward to downward irradiance, are expressed in terms of a particularly convenient pair of parameters, sun altitude and atmospheric transmittance (T). The latter is defined as the ratio of observed downward irradiance to the irradiance at the top of the atmosphere and has not been used before in describing albedo. Examples of albedo values are 0.061±0.005 for heavily overcast skies (0.00.65) of 0.03 for high sun to as large as 0.45 at sun altitudes 25° and increases to 25% for very low sun attitudes. The effect of wind, through ... Abstract An experimental study of the albedo of the sea surface for shortwave solar radiation has been carried out on a fixed platform. Fifteen-minute totals of upward and downward irradiances were recorded continuously for four months over a wide range of atmospheric and sea conditions. The resulting albedo values, the ratio of upward to downward irradiance, are expressed in terms of a particularly convenient pair of parameters, sun altitude and atmospheric transmittance (T). The latter is defined as the ratio of observed downward irradiance to the irradiance at the top of the atmosphere and has not been used before in describing albedo. Examples of albedo values are 0.061±0.005 for heavily overcast skies (0.00.65) of 0.03 for high sun to as large as 0.45 at sun altitudes 25° and increases to 25% for very low sun attitudes. The effect of wind, through ...