danielkoll / pyrads

A line-by-line longwave radiation code for planetary atmospheres.

PyRADS

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 (http://hitran.org/) and the MTCKD continuum model (http://rtweb.aer.com/continuum_frame.html).

Looking for a version of PyRADS that can deal with shortwave radiation (scattering)? https://github.com/ddbkoll/PyRADS-shortwave

References:

(1) Koll & Cronin, 2018, https://doi.org/10.1073/pnas.1809868115.

Installation

1. Download to your own computer.

2. [optional] Install the required libraries using conda:

• cd $PyRADS
• conda env create -f environment.yml
• conda activate pyrads

3. Manually compile the MTCKD model:

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

4. Run test scripts

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

• cd $PyRADS/Test01.olr
• python compute_olr_h2o.py

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

• cd $PyRADS/Test02.runaway
• python compute_olr_h2o.01.100RH.py

Notes

• 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).
• 'environment.yml' assumes you're using a Mac. For Linux, change the gfortran compiler.
• If you're using conda, don't forget to type ``conda activate pyrads'' each time before using PyRADS.
• The current version of PyRADS has a silent bug when using numba + computing line crosssections for multiple species (e.g., H2O + CO2 lines). By default numba is currently disabled. Until the bug is fixed don't use PyRADS + numba without additional validation.
• Dec 2021: PyRADS allows an optional Voigt line profile. The main impact is for opacity calculations at low pressures, where the Lorentz line approximation breaks down. The current Voigt implementation is 3-4x slower than Lorentz lines. To switch line profiles, see OpticalThickness.py.
• Jan 2022: To compute CO2 radiative forcing for Earth-ish climates accurately, suggested spectral resolution is 0.01 cm-1. The impact of Voigt vs Lorentz line shape also becomes much less important at high spectral resolution.

Requirements

Python 3 with numpy and scipy.

For faster calculations: numba.

For the MTCKD continuum model: gmake and gfortran.

Acknowledgements

PyRADS makes use of HITRAN 2016 line lists (http://hitran.org/), AER's MTCKD continuum model (http://rtweb.aer.com/continuum_frame.html), and the PyTran script published by Ray Pierrehumbert as part of the courseware for "Principles of Planetary Climates" (https://geosci.uchicago.edu/~rtp1/PrinciplesPlanetaryClimate/). Brian Rose (http://www.atmos.albany.edu/facstaff/brose/) and Andrew Williams (https://github.com/AndrewWilliams3142) have improved the code.

PyRADS v1.0 is also available on .