== FLEXPART installation guide ==

We know that some people run FLEXPART on MacOS, and it may even be possible to run it under Windows, but usually  it is used under GNU/Linux nowdays.

=== 1. Install dependencies ===

If possible, install the required libraries as packages of your distribution. This will often save you a lot of hassles. On Debian, there is even a package for FLEXPART. Currently, all [https://packages.debian.org/search?keywords=flexpart Debian FLEXPART package] contain version 9.0.2. However, you need to be able to compile the code yourself, so the run-time dependencies installed by this package will not suffice. You need the following dependencies to be fulfilled:

 - `gfortran`
     - or another Fortran compiler - however, then you need to (hand-)compile the libs with exactly the same compiler!
 - GNU `make` (will be installed on
{{{

}}}
 most systems already)
 - `grib_api` lib or its successor, `eccodes`
 - the `jasper` lib (which is needed to use grib_api and eccodes
 - optionally for Versions >= 9.2: `netCDF` Fortran libraries if you want to use the netCDF output feature
 - optionally for Versions >= 10: `openmpi` library if you want to build parallel code

If your distributions offers so-called developer packages for these, you need to install them (they contain the Fortran90 module files which are needed for compilation). They usually pull in the standard packages as well. Thus, on a Debian or Debian-derived system, the following packages should be installed:

{{{
gfortran make libgrib-api-dev libjasper-dev libnetcdf-dev libopenmpi-dev
}}}

=== 2. Review and adapt some parameters ===
Go through `par_mod.f90` and change the parameters if necessary. Typically, this includes the dimensions of the input meteorological data. 

=== 3. Adapt makefile ===

The FLEXPART makefile comes with makefiles. They are inside the source directory. Usually you will need to make some adaptations to your local site.

=== 4. Compile and test ===

Compile the code with the command 

{{{
make -f makefile
}}}
where `makefile` is the makefile which you want to use.

As a first test, you can just start the executable. It should greet you and then stop with a message about missing pathnames (here is an  example with version 8.2.3):

{{{
 Welcome to FLEXPART Version 8.2.3
 FLEXPART is free software released under the GNU General Public License.
  #### TRAJECTORY MODEL ERROR! FILE "pathnames"#### 
  #### CANNOT BE OPENED IN THE CURRENT WORKING #### 
  #### DIRECTORY.                              ####
}}}
 
=== 5. Prepare and test real run ===