RFM Flags
ZEN Flag: ZenithViewing



19OCT18
 Enabled
 Calculate spectra viewing upwards into a plane parallel atmosphere
 *TAN (or *SEC)
section of Driver Table
specifies airmass factor for
calculation (eg, 1.0=vertical, 2.0= 60 deg to vertical)
 Used in combination with FLX flag,
can specify downward fluxes, or transmittances from each level to space.
 Disabled
 Assume other viewing geometry
 Restrictions
 Incompatible with
FOV,
GEO,
GRA,
HOM,
LOS,
NAD,
SFC and
TAB Flags.
 Notes
 Unless an observer altitude is specified
(OBS or
LEV Flags) the observer is assumed to be
at the surface.
 The plane parallel atmosphere allows several simplifications:
no refraction,
no fieldofview effects, analytical CurtisGodson path parameters,
no requirement for altitude coordinate (assuming hydrostatic equilibrium
 see HYD Flag to turn this off).

For upwardviewing calculations with a
spherical atmosphere it is still possible to
use the normal limbviewing calculation but the viewing direction
has to be specified by elevation angle
(replacing *TAN
section label with *ELE and specifying positive elevation angles).
 Use of FLX Flag redefines
ZEN flag.
 Bugs
 Bug#122
(Fixed v4.36)
 Bug#108
(Fixed v4.34)
 Bug#105
(Fixed v4.34)