HR PPart High-Resolution Plane-Parallel atmospheric radiative transfer

Download HR_PPart

Sources: tarball / pgp

The purpose of HR_PPart is to perform radiative transfer computations using high-resolution spectra that have been produced using Kspectrum. Radiative transfer will actually be computed for every wavenumber that defines the input high-resolution spectra. This code is based on analytic radiative transfer solutions that are valid only in the case of a emitting and absorbing, but non-scattering, atmosphere. This code should therefore be used, in the case of the terrestrial atmosphere, for clear-sky LW computations only. However, this code provides the possibility to use cloud data: the scattering optical thickness is then partly integrated in the absorption optical thickness. This is only an approximation, not intended to provide accurate results. Reference results are only achieved for a purely absorbing atmosphere.

Installation

Emission altitude signal in the [500-505] inv. cm spectral range, for a Mid-Latitude Summer standard atmosphere.

Download and extract the archive (tar -zxvf hr_ppart.tgz); then move into the HR_PPart directory, and use the make all command to compile. You should use the make clean command in the case you want to recompile from scratch only (when include files are modified). If only source files are modified, the make all command will recompile modified files.

HR_PPart has been parallelized, which means you will have to launch it using the "mpirun" command:

mpirun -np <NPROCS> ./analytic_RT.exe

with <NPROCS> the number of processes requested for the computation; MacOS users might encounter a error where the OS considers the user requested a number of processes higher than recommended. You can bypass it using the -oversubscribe option:

mpirun -oversubscribe -np <NPROCS>./analytic.exe

Prerequistes: only a fortran compiler is needed (no external libraries). the "gfortran" compiler has been used for development, but other common compilers should work too (ifort, pgfortran, etc.).

Usage

Emission temperature signal in the [500-505] inv. cm spectral range, for a Mid-Latitude Summer standard atmosphere.

Before performing a computation, you should specify where high-resolution spectra of interest are located: you need to provide a link named hires_spectra within the /data directory. This link should be pointing to a directory that contains all spectra produced by Kspectrum for a given atmospheric profile, in addition to the composition.in and molparam.in files used by Kspectrum in order to produce these spectra. This directory should also contain a simple ascii file named profile_parameters.in with the following structure:

Input data for program "analytic_RT"

Temperature of ground (K)
294.0D+0
Temperature of space (K)
3.0D+0
Ground emissivity
1.0D+0

Simulation input is provided through the data.in and options.in files (located in the main HR_PPart directory):

the options.in file provides the possibility to perform a angular integration, or perform a single-direction radiative transfer computation. It provides the possibility to use a specular or a diffuse reflective ground. It provides many options for pre-computing spectral data (collision-induced opacities, water continuum). The last options provide a way to disable the computation of time-consuming results, and also to disable the recording of specific spectral data, which should further speed up the computation.
the data.in file lets the user specify the spectral integration domain, the probe pressure (some results are computed at a given "probe" pressure level) and the direction to use for a single-direction radiative transfer computation.

Results are located into the /results directory; several gnuplot scripts are provided in order to visualise various results.

License

HR_PPart is free software released under the CeCILL v2.1 license. You are welcome to redistribute it under certain conditions; refer to the license for details.