RFM Flags

ZEN Flag: Zenith-Viewing

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
  1. Unless an observer altitude is specified (OBS or LEV Flags) the observer is assumed to be at the surface.
  2. The plane parallel atmosphere allows several simplifications: no refraction, no field-of-view effects, analytical Curtis-Godson path parameters, no requirement for altitude coordinate (assuming hydrostatic equilibrium - see HYD Flag to turn this off).
  3. For upward-viewing calculations with a spherical atmosphere it is still possible to use the normal limb-viewing calculation but the viewing direction has to be specified by elevation angle (replacing *TAN section label with *ELE and specifying positive elevation angles).
  4. Use of FLX Flag redefines ZEN flag.

Bugs
Bug#122 (Fixed v4.36)
Bug#108 (Fixed v4.34)
Bug#105 (Fixed v4.34)