
271Fundamentals of Solar Radiation
© 2008 Taylor & Francis Group, LLC
5.5 Estimation of Terrestrial Solar Radiation
As extraterrestrial solar radiation, I, passes through the atmosphere, a part of it is reected
back into space, a part is absorbed by air and water vapor, and some gets scattered by
molecules of air, water vapor, aerosols, and dust particles (Figure 5.16). The part of solar
radiation that reaches the surface of the earth with essentially no change in direction is
called direct or beam radiation. The scattered diffuse radiation reaching the surface from the
sky is called the sky diffuse radiation.
Although extraterrestrial radiation ...