RFM File Formats

.xsc File: Molecular Cross-Section Data

20JUL17

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
!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]
RFM v5: the original HITRAN format, which is as above but without the !CMNT and *** ... records, can also be used

Fields
FieldTypeDescriptionRange
!CMNT C*80 Comment record(s) (optional) Record starts with '!'
*** C*3 Marker for start of dataset '***'
IDX I Absorber Index See List of Absorbers
NXST I No.of (p,T) tabulations in dataset 1:MAXXST (in rfmsiz.inc)
FMT C*10 Format (optional) ' ' or 'HITRAN2K'
WNLSET R*8 Min.Wavenumber [cm-1] of dataset (optional) >0
WNUSET R*8 Max.Wavenumber [cm-1] of dataset (optional) >0
MOLEC C*10 Chemical Formula (skipped by RFM)
C*20 (HITRAN2K and later)
WNOLOW R*8 Lower Wavenumber [cm-1] for tabulation
WNOUPP R*8 Upper Wavenumber [cm-1] for tabulation
NXSW I No. of Wavenumber points >0
TEM R*4 Temperature [K] of tabulation
PRE R*4 Pressure [Torr] of tabulation 0 treated as 760
XSC R*4 Absorption Cross-Section [cm2/molec]

Notes
  1. The start of each dataset is identified by the first 3 characters in a record being '***' so any records at the start of the file or between one dataset and the start of the next are ignored.
  2. The '***' record is introduced for the RFM, but after that the file structure is that of the data distributed with HITRAN. For RFM v5 the original HITRAN format can also be used The reasons for the additional RFM record are
    1. Identify each molecule by a numerical index IDX - unique and easier to handle than the chemical formulae in the first HITRAN record
    2. List the number of tabulations NXST for a particular wavenumber range - this defines the end of the data being read, and therefore allows files to be concatenated
    3. Identifies the HITRAN format FMT, which was changed with HITRAN2K to allow extra characters (20 instead of 10) for the chemical formula
    4. Provide minimum and maximum wavenumbers for all (p,T) tabulations in datase to save having to read through each dataset.
  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. See program hitxsc for converting HITRAN .xsc data to RFM format, and program makxsc for generating simple .xsc format files from user-supplied data

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)