Estimating solar radiation on sloping surfaces

An important parameter necessary for describing the microclimate or heat budget at the earth's surface is the quantity of incident solar radiation. However, measurements of radiation on other than a horizontal surface are not normally available. This article provides a set of tables listing the ratio of total daily solar energy received on a surface of given aspect and slope to that received on a horizontal surface at latitude 37° 30' S. By multiplying this figure by the total short wave radiation recorded on a horizontal plane subject to similar cloud and atmospheric conditions, daily or monthly values of solar radiation on a sloping surface may be approximated.