TABMRG
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Latest: TABMRG v2.0 (09MAR20)
[Fortran],
v22AUG24 [Python]
| 22AUG24
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Introduction
Part of the RFM handling of Look-Up Tables.
TABMRG is a Fortran90/Python program to manipulate (in the
spectral domain)
RFM-generated look-up tables of pre-tabulated absorption coefficient
(.tab files,
created using the
TAB option).
- Merge files, eg different absorption bands (filling any gaps with 0 values)
- Overwrite part of one file with contents of another
- Extend (with 0 values) or truncate spectral range
- Simply convert from binary to ASCII, or vice-versa
General Comments
- This program can only be used to merge files with the same
molecule/isotope ID and with identical p,T,q axes and
embedded profiles of Temperature and VMR.
Therefore you should create the individual
.tab files using the same RFM
driver tables changing only the spectral range, and you should not
run the TABCMP_X program on the component files
before merging (since this changes the p,T,q tabulation axes).
- The program can be run on either ASCII or binary versions of the
.tab file, and the output can
be either binary or ASCII
- The program asks for an output spectral range which by default is
the minimum range spanning the input files. However it may be useful
to extend the defined range with zero k-values
(see Extending Range), or use this program to reduce
the spectral range.
- Where multiple files are merged, in the case of any spectral overlaps
data from the last file is used.
Installing TABMRG
- Fortran version:
- Download the source code:
[tabmrg.f90]
and the auxiliary modules
[tabaux.f90]
- Compile with any generic FORTRAN compiler, eg
gfortran tabaux.f90 tabmrg.f90 -o tabmrg
NB: if using binary
.tab files
use the same compiler as for the RFM
(see Binary Files).
- Python version:
- Download the Python code
[tabmrg.py]
and the class module
[rfm_tab_class.py]
Running tabmrg
The following is a rather contrived example just designed to show how
the program works.
To run the program, type tabmrg and respond to the prompts
(user-typed responses in red)
tabmrg
R-TABMRG: Running TABMRG v2.0
List of input files, terminated with <CR>
Input file: tab_co.asc_20-50
Input file: tab_co.asc_30-40
Input file: tab_co.asc_60-80
Input file: tab_co.asc_70-90
Input file: <CR>
Summary of spectral ranges to be merged
Index Wavenumber File#
1 2120.0000 1
1000 2129.9900 1
1001 2130.0000 2
2001 2140.0000 2
2002 2140.0100 1
3001 2150.0000 1
3002 2150.0100 Gap - set abs=0
3003 2159.9900 Gap - set abs=0
3004 2160.0000 3
4003 2169.9900 3
4004 2170.0000 4
6004 2190.0000 4
Range of new merged file (<CR>= 2120.0000 2190.0000): 2100 2180
Output file: tab_co.asc_00-80
STOP R-TABMRG: Successful completion
The program should take a few seconds at most, essentially just copying
records from the input files to the output file
Notes
- The example merges 4 input files covering different spectral ranges
(2120-2150 for file#1, 2130-2140 for file#2 etc)
- The Summary lists the structure of the merged data, specifically
where the data source switches from one input file to another.
Index refers to
data points on the underlying fine grid, 0.001 cm-1 in the files
used here.
File# refers to the input file from which the data will be taken
- In this example there is also a gap in the input files from 2150-2160,
the edges of which are also shown in the Summary.
- The output file range is, by default, the range spanned by the
input files, but here the user extends the lower limit down to
2100 cm-1 and truncates the upper limit to
2180 cm-1.
- If the name of the output file contains the string .asc it will
be an ASCII (text) file, .bin will produce a binary file, and if
neither the output file will be the same type as the last input file.
- The output file header starts with an extra comment record indicating
! Merged/extended using program TABMRG v.2.0
but otherwise copies that of the last input file, with the necessary adjustments
to the spectral information.
Extending Range
A .tab file contains a tabulation
of absorption coefficient k [m2/kmol] over a defined
spectral range, νL:νU, represented by the
first and last data records within the file.
When re-used within the RFM as a Look-Up Table
(entered via the *LUT section of the
Driver Table)
the file has to have
a defined range completely spanning the spectral range
(defined in the *SPC section of the
Driver Table) for the RFM
calculation otherwise it will be ignored and the RFM will revert to
using HITRAN (*HIT)
or cross-section (*XSC) data.
For example: the SF6 molecule has a single absorption feature between
925-955 cm-1. If a .tab file
is created spanning just this range, it could not then be used for an RFM
calculation over the range 900-1000 cm-1 since it contains no
information on the SF6 absorption outside 925-955 cm-1
(the equivalent .xsc file which
the RFM will then use by default also only contains the same spectral feature
but the difference is that with .xsc
files the RFM assumes zero absorption outside any tabulated cross-section
data whereas with .tab files it makes
no such assumption).
The crude solution would be to create the initial
.tab file over the wider range,
resulting in a much larger
file containing many records
at high spectral resolution with just
k=0 values
(although this could
then be compressed with the tabcmp_v
program).
The more elegant solution is simply to add four additional spectral
points
of k=0 values, so that the new .tab
file contains the following spectral points
- 900 cm-1 (k=0)
- 924.999 cm-1 (k=0)
- 925-955 cm-1, containing the original values
- 955.001 cm-1 (k=0)
- 1000 cm-1 (k=0)
Thus the file now defines SF6 to have zero absorption beyond the original
tabulated range out to new limits of 900 and 1000 cm-1.
The end values (900 and 1000 cm-1) are supplied by the user
(and there is no advantage in restricting the range if you know that there
are no other SF6 features that can be modelled, eg 0:10000 cm-1
makes the file even more versatile.
The additional records located at 924.999 and 955.001 cm-1
are inserted at intervals ∓δν relative to the original
range νL:νU,
where δν value = 0.001 is the fundamental resolution obtained from
the input file header. This is to ensure that any absorption in, say, the range
900-924.999 cm-1
will be interpolated between two zero records rather than between
zero at 900 cm-1
and whatever k value the original file contained at
925 cm-1.
Filling Gaps
In principle the spectral records of two files can be concatenated
with the RFM then simply interpolating the k value
(actually linearly in ln k) in the gap
from the tabulated k values at the upper wavenumber limit of the
first file ν1U
and the lower limit of the second file ν2L (the
.tab format always stores records in order
of increasing wavenumber).
However this gives unpredictable values of k within the
data gap ν1U:ν2L
since it depends on the tabulated values at the edges of the
component files (although these are presumably small k value if they
represent the edges of physical absorption bands).
A 'gap' is defined as a spectral interval greater than 2δν,
where δν is the fundamental grid spacing of the input file.
When a gap is encountered between
files then two spectral points with k=0 values
are inserted at the borders of the input
file ranges: ν1U+δν, ν2L-δν,
thus defining the absorption between bands to be zero.
Version History
- v2.0 (09MAR20)
- Convert to FORTRAN 90
- v1.21 (05AUG15)
- Change '$' in WRITE statements to avoid gfortran warnings
- v1.2 (24FEB15)
- Improve auto-detection of input file-type
- v1.1 (21DEC14)
- Allow for extra format identifier record in .tab file header
- v1.01 (02DEC14)
- Internal coding changes only, no difference to function.
- v1.00 (04NOV14)
- Original code