This term in beam atmospheric transmittance?
Not quite sure where this fits, but I'll chance it that it goes here.
I've started reading up on the basic science behind solar energy technology, mainly because I find the subject interesting. However, I've come across a term in one of the equations that I'm honestly not sure where it comes from and I can't seem to find it either. It's in the attachments below; "constantdef". The constants being defined are the ones used in the formula for the atmospheric transmittance for beam radiation; "atmostransmit".
The term I'm a bit confused by is A. Basically, I'm hoping that it's a standard notation so that someone else might recognize it. From what I gather from the literature I have, it's a location based constant, but I don't really see where it comes from. Any help on this would be great!
