Impact of Atmosphere on Spectrum

The following figures illustrate how variations in atmospheric conditions affect the direct solar spectrum as modelled by the SPECTRL2 algorithm. Four primary parameters are shown — air mass, precipitable water vapour, turbidity, and ozone — each influencing the shape and magnitude of the spectral irradiance reaching the surface.

Absolute and normalised direct spectrum as calculated by the SPECTRL2 algorithm for different values of air mass (AM).

Direct spectrum determined by the SPECTRL2 algorithm for default atmospheric inputs and varying (a) precipitable water vapour, (b) turbidity at 500 nm, and (c) ozone concentration.