Py4CAtS --- Python for Computational ATmospheric Spectroscopy

lbl2od scheme

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

HItran-GeiSa extract (select) lines of a certain molecule (and isotope) and/or wavenumber range from line parameter database
line-by-line (lbl) cross sections for some molecule(s) and some p, T
computation of line-by-line optical depth due to molecular absorption (combines lbl2xs, xs2ac, ac2od)
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.


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.


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 for easier conversions of physical quantities
Improved 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, acPlot (in module, and odPlot (in module 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 wavenumber shift implemented in fts function
Atmospheric data sets: trace gas profiles saved in separate file
December 2016
Setup script 'generalized' for Windows (pathname construction!)
Line mixing added (first order, Voigt and Lorentz, "brute force" only)
read_line_file in the script now works recursively
atlas now also allows to plot voigtLines new function triSpec for convolution with triangular 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
January 2018
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
Identification / location of path to source files reorganized
(Unix/Linux/...) shell interface adjusted to acArray implementation (and,,
Pressure-induced line shift implemented
June 2018 --- function atlas: recoded to ensure common wavenumber axis for splitted plots functions merge_atmos1D and regrid updated

Summer 2018
Code ported to Python 3 (the Python 2 code is frozen now!)

October 2018 --- a new option cpT to specify the pressure and temperature columns in the pT file,, --- 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) renamed to consistent with the main function of this module
December 2018 --- 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 new function dPlanck_Wavenumber_dT
Module new method strong for subclassed numpy array lineArray
Module info on spectral response added to legend produced by riPlot
Module new method convolve for subclassed numpy array wfArray
March 2019
Module 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 function Triangle corrected
Demo file corrected: mls=atmos1D(...) ---> mls=atmRead(...)

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