PPart_LW

The purpose of PPart_LW is to perform radiative transfer computations using k-distribution data sets (that can be produced by Kdistribution, or any other code). 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.

Brightness temperature in the [4-20] micrometers range, for a Mid-Latitude Summer standard atmospheric profile.

Quick start

Sources: tarball / pgp

Prerequisites

Only a fortran compiler is needed (no external libraries). The gfortran compiler has been used for development.

Installation

Download and extract the archive (tar -zxvf ppart_lw.tgz); then move into the PPart_LW 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.

Run

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

mpirun -np <NPROCS> ./PPart.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> ./PPart.exe

Usage

The code can run either using a pre-computed (and provided) k-distribution data set among 5 standard atmospheric profiles, or from a user-defined spectral data file. This user-defined spectral data file should be name ecrad_opt_prop.txt, and located into the /data directory. The format of this file can be found in the /Doc/gas_opt_prop.pdf documentation file, and a example /Doc/input.for source file provides a fortran subroutine for reading this file. An example ecrad_opt_prop.txt file is provided in the /data directory (for the Mid-Latitude Summer profile).

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

the options.in file provides the possibility to use either a (provided) standard atmospheric data set or a user-defined spectral data set (in this case, the /data/ecrad_opt_prop.txt file has to be found). It provides the possibility to use a specular or diffuse reflective ground, and the possibility to perform the spectral integration over a limited number of spectral intervals. Then the user should specify whether a angular integration should be performed or a single-direction radiative transfer computation is required. Finally, the user can disable the computation of a NER matrix for every spectral interval.
the data.in file lets the user specify the spectral integration domain (if a limited spectral domain should be used), and the direction to use for a single-direction radiative transfer computation. Finally, the user should specify the index of the standard atmospheric profile to use, when the corresponding option has been selected.

Results are located into the /results directory; several gnuplot scripts are provided in order to visualise various results. When a NER matrix has been computed for every spectral interval, a script named anim.bash can be found in the /results/NER_animation directory; this script will produce a animated gif of these NER matrices (the spectral interval evolving with time). This script requires the GraphicsMagick package.

License

PPart_LW is free software released under the GPLv2+ license: GNU GPL version 2 or later. You can freely study, modify or extend it. You are also welcome to redistribute it under certain conditions; refer to the license for details.