RFM File Formats

.xsc File: Molecular Cross-Section Data

13OCT18

Type
Input(s), mandatory if any cross-section molecules used (unless absorption coefficients supplied from look-up tables).

Description
Tabulated cross-section data for one or more heavy molecules (or aerosol extinction).

Filename(s)
Specified in *XSC section of the Driver Table.

Structure
This is the HITRAN format, with the addition of the !CMNT and *** ... records. The HITRAN format files can also be used directly.
!CMNT [optional comment record(s)]
*** IDX NXST [FMT] [WNLSET] [WNUSET] (A3,I7,I10,A10,2F10.4)
MOLEC WNOLOW WNOUPP NXSW TEM(i) PRE(i) [Start repeat for i=1:NXST]
XSC(1,i) XSC(2,i) ...
... XSC(NXSW,i) [End repeat for i=1:NXST]
[eof]

Fields
FieldTypeDescriptionRange
!CMNT C80 Comment record(s) (optional) Record starts with '!'
*** C3 Marker for start of dataset '***'
IDX I Absorber Index See List of Absorbers
NXST I No.of (p,T) tabulations in dataset >0
FMT C10 Format (optional) ' ' or 'HITRAN2K'
WNLSET D Min.Wavenumber [cm-1] of dataset (optional) >0
WNUSET D Max.Wavenumber [cm-1] of dataset (optional) >0

From this point it is standard HITRAN format
MOLEC C20 Chemical Formula
WNOLOW D Lower Wavenumber [cm-1] for tabulation
WNOUPP D Upper Wavenumber [cm-1] for tabulation
NXSW I No. of Wavenumber points >0
TEM R Temperature [K] of tabulation
PRE R Pressure [Torr] of tabulation '0' treated as '760'
XSC R Absorption Cross-Section [cm2/molec]

Notes
  1. The 'RFM' format is the same as the format which can be downloaded from the HITRAN web-site but with the addition of two initial records. The conversion from HITRAN to RFM format can be done with the hitxsc program but, if you're using RFM v5 there is no need to since the HITRAN format can be used directly.
  2. The original HITRAN data is provided as a single spectral file for each (p,T). To use these in the RFM the files have to be concatenated (see Absorption Cross-sections).
  3. WNOLOW,WNOUPP: The RFM doesn't require all tabulations within a dataset to have the same wavenumber grid or resolution. Zero absorption is assumed if any (p,T) datasets have to be extended to WNLSET,WNUSET.
  4. The older data had the pressure PRE set to 0.000, which is taken to indicate atmospheric pressure 760 Torr.
  5. When used for aerosol extinction, the value in the .xsc file is multiplied by the value in the .atm aerosol profile to get the actual extinction, so there is an arbitrary normalisation factor which can be applied to either the cross-section or profile.
  6. Note that there is an older HITRAN format (prior to 2000) which is no longer supported - the easiest way to spot this is that the molecule field in the header record was 10 characters wide instead of 20. If you really do need to use data in this old format, let me know.

Example
Spectrally flat aerosol spectrum over MIPAS range.
***     50         1                                                            
  AEROSOL   685.0000 2410.0000         2     293.0    0.0000  
 1.0000    1.0000

[eof]

Bugs
Bug#116 (Fixed v4.36)
Bug#115 (Fixed v4.35)