RFM Flags: Integration over Solid Angle
FLX Flag



29AUG22
 Enabled
 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
NAD
Flags (see notes below).
 Allows Cooling Rates (COO Flag)
and flux matrices
(MTX Flag) to be derived.
 Disabled
 Spectra calculated along ray paths, per steradian.
 Restrictions
 Notes
 Solid angle integrations are defined as 2 π 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 π u du) =
1/π.
 Integrations are performed using Gaussian 1st moment
quadrature (see Clough et al,
1992).
The number of coefficients
used is controlled by parameter NQAD
in module qadcom_dat.f90, currently set to 4 although values up to
5 are tabulated in gauqad_sub.f90.
 NAD and
ZEN Flags:
when used in conjunction with the FLX flag these define
the hemisphere for integration as follows
 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.
However, note that NAD/ZEN are not used with the MTX flag.
 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
VRT flag)
also converts the
radiances from [nW/cm^{2}...] to [W/m^{2}],
i.e. multiplied by factor 10^{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).
 Bugs
 [none recent]