Py4CAtS --- Python for Computational ATmospheric Spectroscopy

Main Scripts/Functions: From Hitran/Geisa to cross sections to optical depths and radiance (intensity)

higstract: HItran-GeiSa extract (select) lines of a certain molecule (and isotope) and/or wavenumber range from line parameter database
lbl2xs: line-by-line (lbl) cross sections for some molecule(s) and some p, T
lbl2od: computation of line-by-line optical depth due to molecular absorption (combines lbl2xs, xs2ac, ac2od)
(d)od2ri: Given the (layer, delta) line-by-line optical depth solve Schwarzschild equation to radiation intensity

Installation: Getting started with Py4CAtS

Download a tarball of Python sources, some data files, and the documentation and unpack it at some convenient place:
tar xfvz py4CAtS.tgz

The top-level directory py4CAtS includes a 1.ReadMe file with basic instructions, and five subdirectories bin, data, doc, src2, and src3.
(For a transition period there will be two directories with source files for Python 2 and Python 3; however, note that the Python 2 version is essentially frozen since summer 2018)

Prerequisites: Python and numpy (scipy sometimes and matplotlib for plotting)

And you need some line data (HITRAN and/or GEISA). For the beginning, here is a thermal infrared excerpt of Hitran 86.

Usage

Py4CAtS can be used in two ways, from the Unix/Linux (or Windows/Mac?) console/terminal or (much better, more flexible, ..... See the demo !NEW!

or the poster for the ASA-HITRAN 2016 congress) inside the (I)Python interpreter or notebook.

Documentation

For a detailed review of line-by-line modeling for infrared radiative transfer see the manual py4cats.pdf in the doc directory.
Sections 5 and 6 describe Py4CAtS' usage from the Unix/Linux shell and the (i)python shell, respectively.

How to cite Py4CAtS?

F. Schreier and S. Gimeno Garcia. Py4CAtS – Python Tools for Line-by-Line Modelling of Atmospheric Radiative Transfer. In Robert F. Cahalan and Jürgen Fischer (editors), Radiation Processes in the Atmosphere and Ocean (IRS 2012): Proceedings of the International Radiation Symposium (IRC/IAMAS) Volume 1531 of AIP Conference Proceedings, pages 123 - 126. American Institute of Physics, 2013. doi: 10.1063/1.4804723
See also GARLIC (Py4CAtS' big brother)

(download BiBTeX entries)

What's new?

July 2015: The 'main' scripts (e.g. lbl2od) can now be used as functions inside the (I)Python interpreter.
October 2015: Sources thoroughly checked with Pep8, PyFlakes, and PyChecker
Script od2ri with function dod2ri added to compute radiation intensity
March 2016: A new function cgs in module cgsUnits.py for easier conversions of physical quantities
Improved ac2wf.py and od2ri functions/modules.
July 2016: Further source code checks with Pylint; Absorption coefficients and optical depths are now stored in subclassed numpy arrays acArray and odArray (similar to xsArray before)
September 2016: Atmospheric data: corrected "CH3CL" -> "CH3Cl"; Functions atlas (in module lines.py), acPlot (in module absCo.py), and odPlot (in module oDepth.py) rewritten (to exploit recursive calls)
October 2016: xs2ac corrected to allow single level atmosphere and cross sections
November 2016: od2ri corrected to allow atmospheric data starting at ToA; Some further checks of 'important' function arguments implemented; srf.py: wavenumber shift implemented in fts function; Atmospheric data sets: trace gas profiles saved in separate file
December 2016: Setup script py4cats.py 'generalized' for Windows (pathname construction!); Line mixing added (first order, Voigt and Lorentz, "brute force" only); read_line_file in the lines.py script now works recursively; atlas now also allows to plot voigtLines; misc.py: new function triSpec for convolution with triangular; moreFun.py: new function erfcx for exponentially scaled complementary error function
May 2017: Function atmPlot now can plot volume mixing ratios (instead of densities), too.
radiance2radiance clean-up
November 2017: New subclassed numpy array for radiance/intensity (i.e. the radiance array along with its attributes): single return variable of function dod2ri.
New function riPlot and updated/adjusted function riSave to plot and save radiance.
New function truncate in module misc.py
January 2018: atmos1D.py:
New function readVMR to read (trace) gas concentration data (i.e. without pressure and temperature);
Function merge_atmos1D can use pure VMR data as second input.
Atmospheric data sets clean-up, reorganized, ...
March 2018: py4cats.py:
Identification / location of path to source files reorganized; wgtFct.py:
(Unix/Linux/...) shell interface adjusted to acArray implementation; lbl2xs.py (and extract.py, hitran.py, geisa.py):
Pressure-induced line shift implemented
June 2018: lines.py --- function atlas: recoded to ensure common wavenumber axis for splitted plots; atmos1D.py: functions merge_atmos1D and regrid updated
Summer 2018: Code ported to Python 3 (the Python 2 code is frozen now!)
October 2018: lbl2xs.py --- a new option cpT to specify the pressure and temperature columns in the pT file
xs2ac.py, ac2od.py, xs2od.py --- new executable scripts to do these steps from the command line (i.e. "wrappers" for the corresponding functions to be called from the command line / (unix) terminal)
extract.py renamed to higstract.py consistent with the main function of this module
December 2018: radInt.py --- new module defining a subclassed array riArray for radiation-intensity, including functions for read, save, and plot
February 2019: Failed matplotlib imports: raise SystemExit errors replaced by print warnings; Module planck.py: new function dPlanck_Wavenumber_dT; Module higstract.py: new method strong for subclassed numpy array lineArray; Module radInt.py: info on spectral response added to legend produced by riPlot; Module wgtFct.py: new method convolve for subclassed numpy array wfArray
March 2019: Module radInt.py: inconsistencies of header comment lines between riSave and riRead removed; Python 2 sources (in directory src2) removed from tarball
April 2019: broken/incorrect links from bin directory to ../src directory repaired (incorrectly to ../src3); Module srf.py: function Triangle corrected; Demo file corrected: mls=atmos1D(...) ---> mls=atmRead(...)