Spectral attenuation pathway length

The fundamental link between experimental and theoretical research is complementarity. The importance of attenuation models resides in the fact that most locations will not be able to measure their own spectral solar outputs. Attenuation models based on a dynamic database produced from a number of climate profiles, on the contrary, can fit all those climates and almost any other. No attenuation coefficient can dispense with a pathway length estimated using the most accurate methodology available. The author proposes a purely geometric calculation of the pathway length of a monochromatic bundle of collimated rays from the periphery of the atmosphere to the Earth's surface, through layers of different density having different attenuation coefficients. A simplification is offered to the user, who may choose to consider a homogeneous atmosphere with a single layer. The method is supposed to be accurate for any zenith angle. The author expects feedback.