SEC:
Zenith angle is the angle from the vertical, so
sec(zen.ang)=1 for a vertical path, and for slant paths the secant represents the
'air mass factor'.
The same (+ve) definition is used for both
ZEN
and
NAD
directions, although it might be
argued that SEC
values should be negative for downward-viewing.
SECFIL
The type of field is identified by first
using the Fortran INQUIRE statement
to see if it is a file (assumed to be a
.dat file),
in which case the file is opened and the numbers read from the file as if
they were directly inserted within the section at that point.
This can be used in combination with actual numerical fields.
Examples
Downward-viewing calculations for plane-parallel atmosphere
(NAD Flag).
