The variable O3 overwrites the predefined O3 total column concentration from the selected atmospheric model in
MODEL by the user input O3 value (in [atm-cm]).
Typical worldwide and annual O3 concentrations range from 0.15 atm-cm (Ozone depletion at the south pole)
to 0.45 atm-cm, with typical mean values around 0.3 atm-cm.
If the value is not know, user can set O3=-1
(default value) to use the predefined atmospheric model O3 concentration.
In the spectral range covered by 6SV (i.e., 400-2500 nm), O3 absorption mostly contributes in the 475-625 nm spectral range with a typical transmittance of 95% at approximately 550 nm.