*SFC Section | ![]() | ![]() |
RFM Driver Table Sections: Surface Description | 19MAR25 |
Param | Value | Description | Units | Range | Default[1] |
---|---|---|---|---|---|
R | Surface temperature [2] | K | ≥ 0 | Temperature at base of atmosphere | |
R | Surface relative temperature [2] | K | 0 | ||
D | Surface emissivity | 0 – 1 | 1 | ||
or | C193 | File of spectral surface emissivity values [7] | |||
R | Surface altitude [3] | km | Within *HGT profile | Height of base of atmosphere [4] | |
or | |||||
R | Surface pressure [3] | hPa | Within *PRE profile | Pressure of base of atmosphere [4] | |
C | Surface reflectivity model [6] | 'SPECULAR' or 'DIFFUSE' (case insensitive) | 'SPECULAR' |
Since RFM v5.10, the TRA, ABS and OPT output spectra only refer to the direct path atmospheric component (and are therefore the same as would be obtained using the ZEN flag).
This only applies to the downward paths using the plane-parallel atmosphere (NAD flag). Limb paths are treated as usual so will have zero transmittance if fully intersecting the surface. This is to ensure that paths which partially intersect the surface (i.e., with FOV convolution) are treated consistently.
The radiance outputs, i.e. RAD, BBT and RJT output spectra, always include the surface emission and any reflected atmospheric emission as would be expected.
To test whether EMSSFC is a value or a filename, the RFM first attempts to open it as a file. If this fails, a value is assumed. Consequently any fatal error message arising from an incorrect filename/path could be misleading.
Example of a regularly gridded emissivity data file (eg data.sfc from above) in RFM Spectral File Format for regularly gridded data*SFC TEMREL=0.0 ! Equivalent to default value EMSSFC=data.sfc HGTSFC=2.0 ! Set surface at 2km altitude
The same data could be represented as an 'irregularly' gridded file! Surface emissivity spectrum !N.Pts WNO1 WNOD WNO2 5 800.0 50.0 1000.0 0.995 0.996 0.995 0.994 0.993
! Surface emissivity spectrum !N.Pts WNO1 WNOD WNO2 5 800.0 0.0 1000.0 800.0 0.995 850.0 0.996 900.0 0.995 950.0 0.994 1000.0 0.993