The influence of cloud on hourly amounts of total solar radiation at the sea surface

Empirical relations are found for the hourly short‐wave radiation Q received on a horizontal surface at ocean weather station Juliett (52° 30'N, 20°W), for nine categories of cloud, in the form Q = 135 fs (mw hr cm−2) where f = a + b s is the fraction of solar radiation transmitted through the atmosphere, s is the mean of the sines of the solar altitude at the beginning and end of the hour, and a, b are constants. A comparison with a similar analysis of radiation data at station Alfa indicates that the relationships derived for Juliett are valid over a wide band of latitude, and it is shown that they can be used to estimate (within ϕ 10 per cent on most occasions) the total solar radiation received at the sea surface during 5‐day periods over the North Atlantic between 45° and 65°N.