Abstract
When we consider the albedo of the sea surface, the upward light in the sea water, or the emergent light vertically upward from the sea is to be considered in relation to the incident light into the sea. This consideration may also be indispensable not only for the theoretical discussions on the water colour and the transparency, but also for the practical problem such as the application to fishing conditions.
The ratio of the emergent light to the incident light has been investigated theoretically and experimentally by several authors (TAKENOUCHI, VERCELLI). These results showed that this ratio takes different values of a few to several percents. This may be considered due to be dependent on many factors as follows: the sun's altitude, the meteorological conditions such as the cloudiness, the fog and the turbidity of the atmosphere, and also oceanographical conditions such as the state of the sea surface, the turbidity of the sea water, and the stratification of layers in the sea, and so on. Of course, the wave length of the short wave radiation is to be considered, and thus, the problem is too complicated to be solved in a simple manner. However, the purpose of this paper is to give some approaches to the solution of this problem.
The emergent light from the sea is to be considered when we deal with the albedo of radiation over the sea surface. On the basis of some observations conducted by the author, this problem was studied with the theoretical consideration in this paper. The result shows that the ratio of the upward light to the downward light is about 2% in the oceanic water, while it takes much larger values, ranging between 2%-10% in the coastal water, and this may be supposed to be due to the quality of the suspended matter in the sea water.