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A line-by-line longwave radiation code for planetary atmospheres.
Fortran Python
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PyRADS is the Python line-by-line RADiation model for planetary atmosphereS. PyRADS is a radiation code that can provide line-by-line spectral resolution, yet is written in Python and so is flexible enough to be useful in teaching.

For Earth-like atmospheres, PyRADS currently uses HITRAN 2016 line lists ( and the MTCKD continuum model (

Looking for a version of PyRADS that can deal with shortwave radiation (scattering)?


(1) Koll & Cronin, 2018,


  1. Download to your own computer.

  2. Manually compile the MTCKD model:

  • cd $PyRADS/DATA/MT_CKD_continuum/cntnm.H2O_N2/build
  • (on a Mac) make -f make_cntnm osxGNUdbl
  • (on a Mac if you are using gfortran installed with conda) make -f make_cntnm osxGNUCONDAdbl
  1. Run test scripts

To compute outgoing longwave radiation (OLR) in W/m2 for a given surface temperature:

  • cd $PyRADS/Test01.olr
  • python

To compute OLRs for a set of surface temperatures and save the resulting output to txt:

  • cd $PyRADS/Test02.runaway
  • python

NOTE: resolution in test scripts was chosen for relative speed, not accuracy. For research-grade output and model intercomparisons, vertical and spectral resolution need to be increased. For some reference values, see Methods in Koll & Cronin (2018).


Python 2 or 3 with numpy and scipy.

For the MTCKD continuum model: gmake and gfortran.


PyRADS makes use of HITRAN 2016 line lists (, AER's MTCKD continuum model (, and the PyTran script published by Ray Pierrehumbert as part of the courseware for "Principles of Planetary Climates" ( Brian Rose ( has helped improve the code.

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