RRTMGP.jl

RRTMGP.jl is a Julia implementation of the radiative transfer solver RTE (Radiative Transfer for Energetics) and the RRTMGP (RRTM for General circulation model applications—Parallel) correlated-$k$ gas optics (Pincus et al. [1]), based on the reference Fortran implementation rte-rrtmgp. It computes longwave and shortwave fluxes and heating rates for clear, cloudy, and aerosol-laden atmospheres, as well as an analytic gray-radiation mode for idealized studies, on CPUs and GPUs. It is the radiation scheme of the CliMA Earth System Model.

Quick start

Build an idealized atmospheric column, then solve it: gray radiation uses analytic formulas and needs no input data, while the full gas optics loads NCDatasets to download and parse the lookup tables:

using RRTMGP
profile = RRTMGP.standard_atmosphere(Float64; kind = :tropical)
out = RRTMGP.solve(profile; method = RRTMGP.GrayRadiation())  # gray optics
out.heating_rate[1, 1]                          # heating rate at bottom layer [K/s]

2.8935702803079375e-5

using NCDatasets                                # activates the gas optics
out = RRTMGP.solve(profile)                     # clear-sky correlated-k
out.lw_up[end, 1]                                # OLR [W/m²]

282.7005931707845

Code structure

RRTMGP is split into two parts:

Optics computes optical properties and source functions given atmospheric conditions (pressure, temperature, gas concentrations, clouds, aerosols).
RTE computes radiative fluxes given optical properties and source functions.

On top of this functional core sits the RRTMGPSolver, which host models drive through the getter contract, and a standalone front door (solve_gray, standard_atmosphere, solve) for single-column work.

How the documentation is organized

Tutorials (learning-oriented, runnable end to end): A first radiation calculation and Radiative-convective equilibrium (Manabe's classic climate-sensitivity experiment). Start here if you want to learn about radiative transfer and how to run this code.
How-to guides (task-oriented recipes): driving RRTMGP from a host model, running on GPUs, caching the lookup tables, per-band fluxes, and the validated test problems. Start here if you are wiring RRTMGP into a climate model.
Explanation (the concepts and the math): the functional core, the RTE solvers, the optics, and the Fortran and paper concordance for readers coming from rte-rrtmgp.
Reference: the API and the getter contract.

Authors

RRTMGP.jl is being developed by the Climate Modeling Alliance. It is based on RTE+RRTMGP and its reference Fortran implementation, developed by Robert Pincus, Eli Mlawer, and Jennifer Delamere (Pincus et al. [1]).