libRadtran is freely available under the GNU General Public License. To install libRadtran on a Unix type system follow the unpacking instructions and the installation instructions.For the impatient:

1. Get the distribution

MODTRAN Infrared Light in the Atmosphere. About this model. Model Input: Locality: Model Output: Spectrum expanded 5-11-17, changing the IR out value. This version of MODTRAN is designed for use on a PC and incorporates a graphical user interface and comprehensive help files. You might like to begin by opening the manual (see figure below) and walking through Section 1.2 and example CaseM04.ltn. Section 1.2 is a brief tutorial on running MODTRAN and using its input windows. MODTRAN® is a powerful program capable of describing atmospheric absorption, scattering, and emission paths, but it has a complicated computer-card input structure; a custom user interface, PcModWin©, was introduced to minimize setup and error-mitigation issues. NVThermIP automatically runs PcNvMod to calculate the spectrally weighted atmospheric transmission for the sensor to target path. The transmission values are returned to NVThermIP where they are used to calculate target acquisition range. No user interaction is required. PcNvMod is the complete MODTRAN program (PcModWin).

Here is the most recent version 2.0.4 from December 24, 2020.

Older versions are also still available (if asked for username and password, please try libRadtran for both).

If you download the package we ask you to send us a short eMail to let us know that you use the model. We have created a mailing list of libRadtran users in order to notify them of additions, changes, and bug fixes on an irregular basis.

2. Unpack the distribution

3. Compile the distribution

4. Test the program

5. Get additional modules if required

Optical properties of water clouds, ice clouds and OPAC aerosols in netcdf format. Please untar these data in the libRadtran directory. Note that all optical properties data has now been merged into one tar file. If you need the older data, please check here.
Optical properties for ice cloud parameterization based on single scattering data by P. Yang et al., 2013 (updated March 22, 2016). Please untar these data in the libRadtran directory.
Data for the REPTRAN absorption parameterization. Updated December 24, 2017! Please untar these data in the libRadtran directory. Parameterization data for bands as well as for satellite channels is included.
An example for a line-by-line absorption cross section profile for the oxygen A-Band around 760 nm; UVSPEC.O2A.afglms.cdf can be used as molecular_tau_file, see the libRadtran documentation of this option.
For the brave and strong, we also offer line-by-line absorption data for the spectral range 500 nm - 100 micron. Check the README!.
Scripts to compute line-by-line absorption coefficients: Py4CATS
Full resolution extraterrestrial spectrum by Kurucz et al. (1992), 100 MByte!
MOPSMAP - a versatile tool for the modeling of aerosol optical properties - a web interface to generate aerosol optical properties in the netcdf format as required for libRadtran. The user may define size and shape distribution, refractive index, etc. or to use pre-defined aerosol types. The package is described in Gasteiger and Wiegner, 2018.

6. Required software to build libRadtran

The following software is required to successfully compile, link and run all of the libRadtran tools:

GNU make. The compilation might work with other make programs, but usually it doesn't.
The GNU C compiler (gcc). Other compilers might also work.
A Fortran compiler that is compatible with the C compiler. If a C compatible Fortran compiler is not available, f2c will do the job.
Flex - The Fast Lexical Analyzer. Is usually available for all flavours of Linux, under Mac, and for cygwin, but not necessarily installed by default. You may have to select installation of flex manually.
The Perl programming language, version 5.004 or later, is required to run the automatic test.
The netcdf library, including development package.
The GNU Scientific Library (GSL), including development package.

That's it. The example files and the documentation should give you enough knowledge to get started.

Users of Windows 95/98/NTXP/Vista/7 systems are asked to consult the installation of libRadtran under Windows instructions. Compilation under Windows is possible with only little more effort than on a Unix system. Please notice that we haven't updated this README (essentially because of laziness) because the Cygwin Stuff changes continuously - but we are sure that you will find your way!

To test libRadtran on Windows you may also try the Virtual Box. You find detailed installation instructions here.

For users of Windows 10 the Windows Subsystem for Linux is an option which allows installing libRadtran inside the subsystem. When using this subsystem be aware of the differences between Windows and Linux, e.g., with respect to pathnames (case-sensitivity, treatment of spaces, slash vs backslash).

7. Miscellaneous

The standalone version of cdisort 2.1.3 (the C language version of DISORT provided by Tim Dowling, updated July 25, 2013) may be obtained as well. See the included HOW_TO file for tips on installation and usage in a C environment. In publications, please cite Buras et al (2011, J. Quant. Spectr. Ra. Tran. 112, 2028-2034, doi:10.1016/j.jqsrt.2011.03.019).

Download Modtran