FLX Flag: Apply Solid Angle Integration for Flux Calculation
- Transmittance, Absorption and Radiance spectra integrated over solid
angle (but see VRT Flag)
- Values in *TAN (=*LEV)
section of driver table interpreted as atmospheric
levels for output.
- Modifies definitions of ZEN and
Flags (see notes below).
- Allows Cooling Rates (COO Flag)
and flux matrices
(MTX Flag) to be derived.
- Uses Lambertian surface reflections (specular if VRT Flag enabled)
- Spectra calculated along ray paths, per steradian.
- Specular surface reflections
- Incompatible with
- Incompatible with OPT flag unless
VRT flag also enabled
- Either SFC or ZEN flags
must be enabled (but not both).
- Solid angle integrations are defined as 2.pi.x.u.du where
u is the cosine of the zenith angle, integrated from 0:1, and
x is the quantity to be integrated. For transmittances and
absorptions, these are normalised by an factor 1/(2.pi.u.du)=1/pi.
- Integrations are performed using Gaussian 1st moment
quadrature (see Clough et al,
The number of coefficients
used is controlled by parameter NQAD
in subroutine rfmflx.for, currently set to 4 although values up to
5 are tabulated in gauqad.for.
- NAD and
when used in conjunction with the FLX flag these define
the hemisphere for integration as follows
However, note that NAD/ZEN are not used with the MTX flag.
- RAD and COO Flags:
NAD/ZEN are optional and can be used to restrict calculations to the
upward/downward fluxes alone (rather than net fluxes).
- TRA and ABS Flags:
NAD/ZEN are mandatory and define whether the transmittance is from the
output level to the surface/space respectively.
- Sign: upward fluxes are defined as positive, downward as negative.
Cooling rates follow the sign of d(Net Flux)/dz, ie a net flux divergence
(increase in net flux with altitude) gives a positive cooling rate.
- Units: using the FLX flag (without the
also converts the
radiances from nW/cm2 to W/m2, i.e. multiplied by factor 1e-5
- The VRT Flag allows the
solid angle integration
to be suppressed in which case this functions as a simple vertical ray path
calculation (and optical depth calculations are meaningful -
hence OPT flag may also be enabled).