Calculate a full range spectrum¶
We compute the transmittance of an homogeneous, 1-km atmosphere layer at 300 K and 1 atm, with 2% H2O.
This example makes use of a lot of the RADIS optimization and convenience functions :
The database is retrieved from the latest HITRAN data using [HAPI], parsed with RADIS and stored to memory-mapping formats. After the first calls, retrieving the database will be very fast
The RADIS algorithm includes a sparse wavenumber implementation, which is activated by default in the following example where the waverange is very large. This behavior can be changed by setting the
SPARSE_WAVENUMBERkey of theradis.configdictionary, or of the ~/radis.json user file.The wavenumber grid is automatically computed using the
wstep='auto'parameter.A linestrength cutoff reduces the initial number of lines.
Eventually, the full-range spectrum (about 4.8M points) is computed within a minute, with about 140k lines resolved, i.e. a performance of about 1e10 gridpoints*lines/s.
Extra optimization could be achieved by cutting the spectrum in small intervals, but requires an a-priori knowledge of the absorption & emission ranges of the spectrum. See the Calculate a large spectrum by part
import astropy.units as u
from radis import calc_spectrum, config
# This next line is needed, because the brodening coefficient of H2O by CO2 is not known.
config["MISSING_BROAD_COEF"] = "air"
s = calc_spectrum(
wmin=0.5 * u.um,
wmax=15 * u.um, # cm-1
mole_fraction={
"CO2": 425.48e-6,
"H2O": 0.02,
}, # CO2 as of August 2025, see https://gml.noaa.gov/ccgg/trends/
isotope="1,2,3",
pressure=1.01325, # bar
Tgas=300, # K
path_length=1e5, # 1 km in cm
verbose=2,
databank="hitran",
wstep="auto",
)
--------------------------------------------------------------------------------
CO2 - HITRAN - Downloading database
--------------------------------------------------------------------------------
Download:
- All files already downloaded.
Caching to HDF5/H5 format:
- All files already cached.
HAPI version: 1.3.0.0
HAPI version: 1.3.0.0
HAPI version: 1.3.0.0
... 0.00s - Check line databank
... 0.00s - Reinitialize database
... Scaling equilibrium linestrength
... 0.01s - Scaled equilibrium linestrength
Discarded 80.47% of lines (linestrength<1e-27cm-1/(#.cm-2)) Estimated error: 0.00%
... 0.02s - Applied linestrength cutoff
/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/master/radis/misc/warning.py:427: MissingSelfBroadeningTdepWarning: Self-broadening temperature coefficient `Tdpsel` not given in database: used `Tdpair` instead
warnings.warn(WarningType(message))
... 0.01s - Calculate broadening HWHM
... 0.00s - Calculated lineshift
Sparsity (grid points/lines) = 8.4. Set sparse_ldm to True
... 0.00s - Generated Wavenumber Arrays
... Calculating line broadening (64086 lines)
Estimated time for calculating broadening: 4.80s on 1 CPU
... 0.36s - Calculated line broadening
... 0.02s - Calculated other spectral quantities
... 0.42s - Spectrum calculated (before object generation)
Calculating Equilibrium Spectrum
Physical Conditions
----------------------------------------
Tgas 300 K
isotope 1,2,3
mole_fraction 0.00042548
path_length 100000.0 cm
pressure 1.01325 bar
self_absorption True
species CO2
state X
wavenum_max 19994.4221 cm-1
wavenum_min 666.4850 cm-1
Computation Parameters
----------------------------------------
Tref 296 K
add_at_used numpy
broadening_method voigt
cutoff 1e-27 cm-1/(#.cm-2)
dbformat hitran
dbpath /home/docs/.radisdb/hitran/CO2.h5
diluent air
folding_thresh 1e-06
include_neighbouring_lines True
isatom False
isneutral None
lbfunc None
memory_mapping_engine auto
neighbour_lines 0 cm-1
optimization simple
parsum_mode full summation
pfsource default
potential_lowering None
pseudo_continuum_threshold 0
sparse_ldm True
truncation 50 cm-1
waveunit cm-1
wstep 0.036 cm-1
zero_padding 536889
Config parameters
----------------------------------------
Information
----------------------------------------
chunksize None
db_use_cached True
dxG 0.1375350788016573
dxL 0.20180288881201608
export_lines False
export_populations None
export_rovib_fraction True
levelsfmt None
load_energies False
lvl_use_cached True
parfuncpath None
total_lines 328081
warning_broadening_threshold 0.01
warning_linestrength_cutoff 0.01
wavenum_max_calc 19994.4221 cm-1
wavenum_min_calc 666.4850 cm-1
----------------------------------------
... 0.00s - Generated Spectrum object
0.43s - Spectrum calculated
--------------------------------------------------------------------------------
H2O - HITRAN - Downloading database
--------------------------------------------------------------------------------
Download:
- Downloading all isotopes for H2O
Downloading isotopes: 0%| | 0/9 [00:00<?, ?it/s]
Downloading isotopes: 11%|█ | 1/9 [00:09<01:13, 9.16s/it]
Downloading isotopes: 22%|██▏ | 2/9 [00:10<00:33, 4.79s/it]
Downloading isotopes: 33%|███▎ | 3/9 [00:12<00:19, 3.20s/it]
Downloading isotopes: 33%|███▎ | 3/9 [00:13<00:27, 4.54s/it]
/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/master/radis/io/hitran.py:224: UserWarning: ValueError encountered during download. Retrying (attempt 1/2)...
ldb.download_and_parse(
Downloading isotopes: 0%| | 0/9 [00:00<?, ?it/s]File already exist: /home/docs/.radisdb/hitran/downloads__can_be_deleted/H2O/H2O_1.data. Deleting it.`
Downloading isotopes: 11%|█ | 1/9 [00:08<01:11, 8.92s/it]File already exist: /home/docs/.radisdb/hitran/downloads__can_be_deleted/H2O/H2O_2.data. Deleting it.`
Downloading isotopes: 22%|██▏ | 2/9 [00:10<00:34, 4.88s/it]File already exist: /home/docs/.radisdb/hitran/downloads__can_be_deleted/H2O/H2O_3.data. Deleting it.`
Downloading isotopes: 33%|███▎ | 3/9 [00:12<00:20, 3.37s/it]File already exist: /home/docs/.radisdb/hitran/downloads__can_be_deleted/H2O/H2O_4.data. Deleting it.`
Downloading isotopes: 44%|████▍ | 4/9 [00:14<00:13, 2.77s/it]
Downloading isotopes: 56%|█████▌ | 5/9 [00:15<00:08, 2.03s/it]
Downloading isotopes: 67%|██████▋ | 6/9 [00:15<00:04, 1.53s/it]
Downloading isotopes: 78%|███████▊ | 7/9 [00:16<00:02, 1.35s/it]
Downloading isotopes: 100%|██████████| 9/9 [00:16<00:00, 1.85s/it]
HITRAN database download complete
Added HITRAN-H2O database in /home/docs/radis.json
HAPI version: 1.3.0.0
HAPI version: 1.3.0.0
HAPI version: 1.3.0.0
... 0.00s - Check line databank
... 0.00s - Reinitialize database
... Scaling equilibrium linestrength
... 0.01s - Scaled equilibrium linestrength
Discarded 73.13% of lines (linestrength<1e-27cm-1/(#.cm-2)) Estimated error: 0.00%
... 0.02s - Applied linestrength cutoff
/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/master/radis/misc/warning.py:427: MissingSelfBroadeningTdepWarning: Self-broadening temperature coefficient `Tdpsel` not given in database: used `Tdpair` instead
warnings.warn(WarningType(message))
... 0.01s - Calculate broadening HWHM
... 0.00s - Calculated lineshift
Sparsity (grid points/lines) = 61.9. Set sparse_ldm to True
... 0.01s - Generated Wavenumber Arrays
... Calculating line broadening (78011 lines)
Estimated time for calculating broadening: 260.28s on 1 CPU
... 35.97s - Calculated line broadening
... 0.15s - Calculated other spectral quantities
... 36.17s - Spectrum calculated (before object generation)
Calculating Equilibrium Spectrum
Physical Conditions
----------------------------------------
Tgas 300 K
isotope 1,2,3
mole_fraction 0.02
path_length 100000.0 cm
pressure 1.01325 bar
self_absorption True
species H2O
state X
wavenum_max 19994.4221 cm-1
wavenum_min 666.4850 cm-1
Computation Parameters
----------------------------------------
Tref 296 K
add_at_used numpy
broadening_method voigt
cutoff 1e-27 cm-1/(#.cm-2)
dbformat hitran
dbpath
diluent air
folding_thresh 1e-06
include_neighbouring_lines True
isatom False
isneutral None
lbfunc None
memory_mapping_engine auto
neighbour_lines 0 cm-1
optimization simple
parsum_mode full summation
pfsource default
potential_lowering None
pseudo_continuum_threshold 0
sparse_ldm True
truncation 50 cm-1
waveunit cm-1
wstep 0.004 cm-1
zero_padding 4831986
Config parameters
----------------------------------------
Information
----------------------------------------
chunksize None
db_use_cached True
dxG 0.1375350788016573
dxL 0.20180288881201608
export_lines False
export_populations None
export_rovib_fraction True
levelsfmt None
load_energies False
lvl_use_cached True
parfuncpath None
total_lines 290304
warning_broadening_threshold 0.01
warning_linestrength_cutoff 0.01
wavenum_max_calc 19994.4221 cm-1
wavenum_min_calc 666.4850 cm-1
----------------------------------------
... 0.04s - Generated Spectrum object
36.21s - Spectrum calculated
/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/master/radis/misc/warning.py:427: UnevenWaverangeWarning: When resampling the spectrum, the new waverange had unequal spacing.
warnings.warn(WarningType(message))
/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/master/radis/misc/warning.py:427: UnevenWaverangeWarning: When resampling the spectrum, the new waverange had unequal spacing.
warnings.warn(WarningType(message))
CO2-hitran-300K-#3728 new quantities added: ['emisscoeff']
H2O-hitran-300K-#2368 new quantities added: ['emisscoeff']
Plot low and high resolution spectra on the same graph :
s.apply_slit(10, "nm")
import matplotlib.pyplot as plt
plt.figure(figsize=(16, 6))
s.plot("transmittance_noslit", wunit="nm", color="k", alpha=0.1, nfig="same")
s.plot("transmittance", wunit="nm", color="k", nfig="same")
<matplotlib.lines.Line2D object at 0x72085fce0830>
Print some details about the computed spectrum :
We could also simply use print(s)
print("Number of grid points: ", len(s))
print(
"Number of lines: ", s.c["total_lines"]
) # some are discarded by linestrength cutoff
print("Number of lines: ", s.c["lines_calculated"])
print("Whether the sparse wavenumber algorithm was activated: ", s.c["sparse_ldm"])
print(f"Lineshape truncation used: {s.c['truncation']:.1f}cm-1")
print(f"Total calculation time: {s.c['calculation_time']:.1f}s")
print(
f"Gridpoints * lines/s : {len(s)*s.c['lines_calculated']/s.c['calculation_time']:.1e}"
)
Number of grid points: 4831986
Number of lines: 618385
Number of lines: 142097
Whether the sparse wavenumber algorithm was activated: True
Lineshape truncation used: 50.0cm-1
Total calculation time: 36.6s
Gridpoints * lines/s : 1.9e+10
Total running time of the script: (1 minutes 21.306 seconds)