pyharp-plot CLI

pyharp-plot is the unified command line entry point for spectroscopy diagnostic figures. It can plot HITRAN collision-induced absorption (CIA) binary coefficients, molecular cross sections, attenuation coefficients, transmission, and multi-panel overview PDFs.

Basic Usage

Choose one subcommand, then choose the target data source with --pair, --species, or --composition where that subcommand supports it.

pyharp-plot binary --pair H2-H2 --temperature-k 300 --wn-range=20,10000
pyharp-plot xsection --species CO2 --temperature-k 300 --pressure-bar 1 --wn-range=20,2500
pyharp-plot attenuation --species H2O --temperature-k 300 --pressure-bar 1 --wn-range=25,2500
pyharp-plot transmission --composition H2O:0.1,H2:0.9 --temperature-k 300 --pressure-bar 1 --path-length-km 1 --wn-range=25,2500
pyharp-plot overview --species H2O --temperature-k 300 --pressure-bar 1 --path-length-km 1 --wn-range=20,2500

Every command writes a figure. Use --figure to select an explicit output path. Without --figure, plots are written under output/ using a name derived from the target, plot type, temperature, pressure, and wavenumber range, such as output/co2_xsection_300K_1bar_20_2500.png.

Subcommands

binary

Plot a HITRAN CIA binary absorption coefficient spectrum. This subcommand uses a CIA pair selected by --pair.

pyharp-plot binary --pair H2-H2 --temperature-k 300 --wn-range=20,10000
pyharp-plot binary --pair H2-He --temperature-k 500 --resolution 5 --figure output/h2_he_cia.png

xsection

Plot a molecular absorption cross section at one pressure-temperature state. This subcommand uses a molecule selected by --species.

pyharp-plot xsection --species CO2 --temperature-k 300 --pressure-bar 1 --wn-range=20,2500
pyharp-plot xsection --species CH4 --temperature-k 700 --pressure-bar 0.1 --wn-range=1000,4000 --refresh-hitran

attenuation

Plot an attenuation coefficient in 1/m. Select exactly one target:

• --pair for a CIA pair.

• --species for a molecule.

• --composition for a gas mixture.

pyharp-plot attenuation --pair H2-H2 --temperature-k 300 --pressure-bar 1 --wn-range=20,10000
pyharp-plot attenuation --species CO2 --temperature-k 300 --pressure-bar 1 --wn-range=20,2500
pyharp-plot attenuation --composition H2O:0.1,H2:0.9 --temperature-k 300 --pressure-bar 1 --wn-range=25,2500

transmission

Plot transmission over a fixed path length. Select exactly one target with --pair, --species, or --composition. The path length defaults to 1 km and can be changed with --path-length-km.

pyharp-plot transmission --pair H2-H2 --temperature-k 300 --pressure-bar 1 --path-length-km 1 --wn-range=20,10000
pyharp-plot transmission --species CO2 --temperature-k 300 --pressure-bar 1 --path-length-km 0.5 --wn-range=20,2500
pyharp-plot transmission --composition H2O:0.1,H2:0.9 --temperature-k 300 --pressure-bar 1 --path-length-km 1 --wn-range=25,2500

overview

Generate a multi-panel PDF. With one species and one wavenumber range, the output is a single molecule overview. With multiple species or multiple --wn-range values, the output is a combined multi-page PDF. With --composition, the output is an atmospheric mixture overview PDF and a manifest JSON file.

pyharp-plot overview --species H2O --temperature-k 300 --pressure-bar 1 --path-length-km 1 --wn-range=20,2500
pyharp-plot overview --species H2O CO2 CH4 --temperature-k 500 --pressure-bar 0.5 --wn-range=25,2500 --wn-range=2500,10000
pyharp-plot overview --composition H2O:0.1,H2:0.9 --temperature-k 300 --pressure-bar 1 --wn-range=25,2500 --manifest output/h2o_h2_sources.json

Shared Options

--wn-range=min,max

Wavenumber bounds in cm^-1. CIA plots default to 20,10000 when it is omitted. Molecular and mixture plots default to 20,2500. The overview subcommand accepts this option more than once.

--resolution value

Wavenumber grid spacing in cm^-1. The default is 1.

--temperature-k value

Temperature in kelvin. The default is 300.

--pressure-bar value

Pressure in bar. The default is 1 for subcommands that use pressure.

--hitran-dir path

Directory used for downloaded HITRAN line and CIA data. The default is hitran.

--refresh-hitran and --refresh-cia

Re-download cached HITRAN line or CIA data.

--cia-index-url url

HITRAN CIA index URL. The default is https://hitran.org/cia/.

--figure path

Explicit figure path. Use .png for single plots and .pdf for overview plots.

Target Selection

Use --pair for a CIA pair, for example H2-H2 or H2-He. Built-in CIA pair resolution includes CH4-CH4, CO2-CH4, CO2-CO2, CO2-H2, H2-H2, H2-He, N2-CH4, and N2-N2.

Use --species for molecular line calculations. Built-in HITRAN line species are CH4, CO2, H2, H2O, and N2.

Use --composition for a gas mixture. The format is a comma-separated list of species:fraction terms:

--composition H2O:0.1,H2:0.9

For attenuation and transmission, choose only one of --pair, --species, and --composition. For overview, choose only one of --species and --composition.

Output Examples

Default filenames are normalized for shells and filesystems:

pyharp-plot xsection --species CO2 --temperature-k 275.5 --pressure-bar 0.25 --wn-range=25,30.5
# writes output/co2_xsection_275p5K_0p25bar_25_30p5.png

pyharp-plot overview --composition H2O:0.1,H2:0.9 --wn-range=25,2500
# writes output/h2o_0p1_h2_0p9_overview_300K_1bar_25_2500.pdf
# also writes output/h2o_0p1_h2_0p9_overview_300K_1bar_25_2500.manifest.json