RFM File Formats

.hit File: HITRAN Binary Line Data

04DEC17

Type
Input, mandatory if any line molecules (molecules ID#1:99) used (unless absorption coefficients supplied from look-up tables).

Description
HITRAN 'line' data converted into direct-access binary format.
For RFM v5.0 the original HITRAN .par file (ASCII, 160 characters per record) may be used instead

Filename
Specified in *HIT section of Driver Table

Structure
Direct access binary file with record length 88bytes
5 different types of record determined by value of 1st field LSTAT
Rec# Fields LSTAT Description
1 LSTAT MAXMOL IREC1 IREC2 HEAD48 0 File Header
2:IREC1-1 LSTAT HEAD84 4 Comments
IREC1:IREC1+3 LSTAT IDXOFF IDUMMY WNUM IFWDPT(1) IFWDPT(2) ... IFWDPT(14) -7 Forward Pointer Block
IREC1+4:IREC2-1 LSTAT IDXMOL ISO WNUM STREN TPROB ABROAD SBROAD ELS ABCOEFF TSP IUSGQ ILSGQ USLQ BSLQ AI REF >9 Line Parameters
IREC2 LSTAT IDUMMY IDUMMY WNUM -2 File Termination
Forward Pointer Blocks of 4 records are also interspersed with the Line Parameter records at regular intervals throughout the file

Fields
The following fields are specific to the binary format, not part of the HITRAN ASCII data
FieldTypeDescriptionAllowed Range
LSTAT I*4 Record-type identifier -7,-2,0,4, or >9
MAXMOL I*4 Max. No. different molecules in file (n x 14) (usually 56)
IREC1 I*4 Rec# of first data record
IREC2 I*4 Rec# of last data record
HEAD48 C*48 File description, etc
HEAD84 C*84 Further file description, etc
IDXOFF I*4 HITRAN Index of 1st mol. in FP record 1, 15, 29 or 43
IDUMMY I*4 Dummy value (to main record structure) 0
IFWDPT I*4 No.records to skip before next mol#(IDXOFF-1+i) >0
The following fields are taken from the HITRAN ASCII Data
FieldTypeDescriptionRange/Units
WNUM R*8 Wavenumber [cm-1]
IDXMOL I*4 HITRAN index of molecule 1:MAXMOL
ISO I*4 HITRAN isotope# >0
STREN R*4 Line strength [cm-1/(kg.moles.cm-2)] @296K
TPROB R*4 Transition Probability [Debyes2]
ABROAD R*4 Air-broadened halfwidth (HWHM) [cm-1/atm] @ 296K
SBROAD R*4 Self-broadened halfwidth (HWHM) [cm-1/atm] @ 296K
ELS R*4 Lower State Energy [cm-1]
ABCOEF R*4 Coefficient of T-dependence of ABROAD -
TSP R*4 Transition shift due to pressure [cm-1/atm]
IUSGQ I*4 Upper state global (=Vib) quantum index -
ILSGQ I*4 Lower state global (=Vib) quantum index -
USLQ C*9 Upper state local (=Rot) quantum state ID -
BSLQ C*9 Lower state local (=Rot) quantum state ID -
AI C*3 Accuracy indices for freq, strength, halfwidth -
REF C*6 References for freq, strength, halfwidth -

Notes
  1. HITRAN ASCII files can be converted to binary format with the hitbin program
  2. As with the ASCII files the 'line parameter' records in the binary file are ordered by increasing wavenumber.
  3. All records between IREC1:IREC2 can be read as 3 (dummy) integers followed by a valid local WNUM value, including the Forward Pointer and File Termination records. This is to allow a particular wavenumber in the file to be found rapidly, eg with a binary search, by testing only the WNUM value for each record.
  4. The main difference between the structure of the binary file and the original ASCII data is the use of forward pointers IFWDPT to help navigation. Within each Line Parameter record, IFWDPT is the number of records to skip until the next line (at higher wavenumber) for the same molecule. This makes it much faster to select lines from only a subset of the molecules in the file.
  5. In addition to the forward pointers within each transition, at the start of the binary file and interspersed (eg every 200 records) throughout are 'forward pointer blocks' of 4 records, each record containing forward pointers IFWDPT for 14 molecules, hence molecules 1:56 (=MAXMOL). The idea is that you can enter the file at any point, step backwards until you find a forward pointer block (maximum of 200 records) and then be guaranteed to have pointers to the next location of records for every molecule.
  6. The default LSTAT value for Line Parameter records is 10. The program hitbin.f allows different datasets to be merged with the newer data having a higher LSTAT value (and the old line removed), while the original GENLN2 conversion program hitlin kept the old lines but set LSTAT negative. Either way, the RFM will ignore any lines with LSTAT <10.
  7. STREN: Line Strengths in the original HITRAN ASCII data are defined as [cm-1/(kg.molec.cm-2)]. These are multiplied by Avogadro's Number ( 6.0221367E26 ) for the binary file in order to ensure that the numbers are in the normal range which can be represented by exponentials.
  8. The following fields are not actually used within the RFM: ELS, TPROB, USLQ, AI, REF
  9. BSLQ is only used in conjunction with CO2 Line-mixing (MIX Flag)
  10. RFM v5 can use the original 160-character HITRAN .par files, although this is less efficient since it had to read through the file sequentially 3 times. Basically, if you find yourself waiting for the RFM to run, you should consider running the hitbin program to convert to binary
  11. Line-mixing (MIX Flag) and non-LTE (NTE Flag) calculations require a binary file since these use additional fields inserted by the hitbin program.