RFM File Formats

.tab File: Tabulated Absorption Coefficient File

29SEP05

Type
Output(s), if TAB Flag enabled.
Optional Input(s) if LUT Flag enabled (alternative to .lut files).

Description
Absorption Coefficients [m2/mole] tabulated as function of -ln(pressure) and temperature.

Filename(s)
Default is tab_[s][g].asc where [s] is the spectral range and [g] is the gas
Different names may be specified in the *TAB section of the Driver Table.

Structure
!HEADER1
!HEADER2
!HEADER3
MWCODE ID[.ISO] TAB
NL NV V1 DV NP P1 DP NT T1 DT
[ HEXGRD(j) ] If NV <0, Repeat for j=1:(|NV|/200)+1
K(1,i) K(2,i) ...
... K(NX,i) Repeat for i=1:NV, or (NL <0) 1:NG
[eof]

Fields
FieldTypeDescriptionActual Values
!HEADER1 C*80 Spectrum type, ray-path and RFM version ID
!HEADER2 C*80 Text read from *HDR section of Driver Table
!HEADER3 C*80 Captions for NL ... record
MWCODE C*8 Microwindow Label Matches LABSPC
IDX I HITRAN Index of absorber See List of Absorbers
.ISO I (optional) '.' then HITRAN Isotope# See List of Isotopes
TAB C*3 Tabulation Function 'LIN'
NL I No. of Singular Values 0
NV I No. of Wavenumber Points >0, <0 if irreg. grid included
V1 R*8 Lowest Wavenumber [cm-1]
DV R*8 Wavenumber Increment [cm-1]
NP I No. of -ln(p) Points >0
P1 R*4 Lowest -ln(p) (p in [mb])
DP R*4 -ln(p) increment
NT I No. of Temperature Points >0
T1 R*4 Lowest Temperature [K]
DT R*4 Temperature increment [K]
HEXGRD Z*1 1 hex character=4 grid points
K R*4 K(NX,NV) Matrix, NX=NP*NT R*8 with DBL Flag

Notes
  1. The first 3 HEADER records .tab files are similar to RFM Spectral Files, and the next two records are similar to .lut files. (but distiguished by the value NL=0).
  2. Each record represents all the (p,T) points for a single wavenumber grid point. In binary format (BIN Flag enabled) each record therefore contains NX=NP*NT Real values (P index increasing before T index).
  3. When creating isotopic .tab files (see Notes on use of the TAB Flag) a separate file is created for each isotopic profile supplied in the *ATM section. These have "iN" where N is the isotope number, inserted into the output filename (eg a profile *CH4(2) will result in a .tab filename ...ch4i2...). There will also be a file "i0" for remaining, unspecified isotopes (which may contain all zeros if all isotopes were specified - consider this a "feature" of the RFM). This information is also inserted into the [.ISO] as a decimal value after the IDX value, eg "06.2" and "06.0".
  4. When using .tab files as input to RFM calculations, if no isotopic profile is specified the RFM will only accept a generic .tab file for that molecule (eg with the ID " 6" rather than " 6.x"). Conversely, if isotopic profiles are specified the RFM will only accept .tab files for that particular isotope (eg with the ID "6.2") and any unspecified isotopes will be modelled using the default isotopic file (eg "6.0"). , Note: if, for example, you generate .tab files for the first two isotopes (6.1, 6.2) the remaining isotopes will be included in the file with ID 6.0. However, if you then use these as input to the RFM specifying only the first isotope, 6.1, as a separate profile, the RFM will incorrectly assume that isotope#2 is included in the default file 6.0 and ignore the file 6.2.
  5. Although the RFM will create .tab files with the k-coefficient tabulated directly (TAB = 'LIN') it is possible to use different tabulations as input files, as described for the .lut files.
  6. By default, .tab files are generated on a regularly spaced wavenumber grid. However, it is possible to supply the RFM with an irregular spectral grid (.grd file). In this case the grid information is also included in the output .tab file, indicated by a negative value of NV. The absolute value of NV still represents the number of regularly spaced grid points spanned by the output file, but only NG points from the irregular grid are actually written.
  7. The irregular grid is represented by records of up to 50 hexadecimal characters HEXGRD, each character representing 4 regularly spaced grid points at resolution DV - see .grd file format. Thus NG is the number of 'set' bits in the grid.
  8. When using .tab files based on irregular spectral grids as input, the grid information is automatically used by the RFM to linearly interpolate the data to the RFM internal grid (which may be regularly spaced). This is distinct from using the GRD Flag which specified an irregularly spaced RFM internal grid.

Example
 ! o3      Tabulated Absorp.Coeff. created by RFM v.3.42_OXF
 !  TEST
 !NL  NV    V1      DV    NP   P1         DP         NT       T1          DT
O3__0053  3 LIN
 0  2701 1036.0250 0.0005 20  -6.907755   0.727132    8     120.000      30.000
   22.20402       26.26059       26.64072       19.32595       11.47375
   6.571761       3.676178       1.906070      0.9411216      0.4572936
...
[eof]