Monthly Averages of the Daily Effective Optical Air Mass and Solar Related Angles for Horizontal or Inclined Surfaces

Abstract

An analytical method is described for calculating the daily averages or effective values of the sun’s elevation, azimuth, hour angle, angle of incidence and air mass. A particular case is considered first and corresponds to the extraterrestrial radiation. The general derivation takes into account atmospheric effects in a simple way, provided that long-term averages of solar radiation are available. Examples of application are given for the climate of Montreal, Canada. In particular, it is shown that monthly averages of beam radiation on the horizontal may be directly converted to normal incidence values (and vice versa) by use of the mean solar elevation.