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last modified 2013-09-30 14:15

The homepage of FLEX ART and FLEXTRA at the Norwegian Institute for Air Research (NILU)


The FLEXPART model is a Lagrangian Particle Dispersion Model developed at the Norwegian Institute for Air Research in the Department of Atmospheric and Climate Research. The model development team consists of Andreas Stohl (who originally wrote FLEXPART), Sabine Eckhardt, Harald Sodemann, and John Burkhart.

FLEXPART is free software released under the GNU General Public License V3.0

The FLEXPART license is available here: [ FLEXPART-GPL ]


FLEXTRA and FLEXPART are an atmospheric trajectory and a particle dispersion model, respectively, that are used by a growing user community. A recent user survey resulted in 35 groups from 17 countries who have confirmed to actively use one of the models for a variety of research purposes. There are also a few operational installations for emergency preparedness and similar objectives. If you are using FLEXTRA or FLEXPART but are not on the list, please contact Andreas Stohl and provide the relevant details.

FLEXTRA and FLEXPART can be driven with meteorological input data from a variety of global and regional models, most commonly from the European Centre for Medium Range Weather Forecasts (ECMWF). They run on a variety of Unix/Linux and PC platforms where a Fortran 77/90 compiler and a GRIB decoding library is installed. Applications of the models cover topics like transport of radionuclides after nuclear accidents, pollution transport, greenhouse gas cycles, stratosphere-troposphere exchange, water cycle research, and others, as shown by a list of publications for which FLEXTRA or FLEXPART were used.

Both models are freeware and can be downloaded from this webpage. I appreciate if the users can inform me on any installations. FLEXTRA is a mature code that currently isn't undergoing further development; however, FLEXPART is being developed continuously. Therefore, if useful model code or code for the pre/post-processing of the input/output data is developed, it would be nice if it could be shared with the FLEXTRA/FLEXPART user community. If you have code that you think others might find useful, you can also send it to me and I can put it on this webpage. One source code package of FLEXPART can be used for ECMWF as well as GFS input data. Many people have contributed to the model development over the years, including Sabine Eckhardt, Harald Sodemann, John Burkhart, Caroline Forster, A. Frank, Gerhard Wotawa and Petra Seibert.

For a better understanding of the concept and details of FLEXPART, read this journal article from Atmospheric Chemistry and Physics: Technical note: The Lagrangian particle dispersion model FLEXPART version 6.2.

FLEXPART source code download

FLEXPART for input data from global models (ECMWF, GFS)

Source code Documentation (PDF) Description
FLEXPART V9.02 in Fortran 90 for GFS and ECMWF
BUGFIX in gridcheck_gfs.f90 xaux2 was set wrong - Revision 151
FLEXPART V9.01 in Fortran 90 for GFS and ECMWF
BUGFIX in concoutput_nest, added missing use statement in gridcheck - Revision 147
FLEXPART V9.0 in Fortran 90 for GFS and ECMWF
Thanks to P. Kaufmann, M. Schraner (Meteoswiss) and S. Henne (EMPA), for the conversion to FORTRAN 90, January 2012 (Revision 144 - see log files)
FLEXPART V8.23 for GFS and ECMWF User guide V8.2 Bug correction in verttransform - thanks to Stephan Henne, August 2011
FLEXPART V8.22 for GFS and ECMWF User guide V8.2 May 2011
FLEXPART V8.2 for GFS and ECMWF User guide V8.2 Nov 2010 (read about changes)
FLEXPART V8.1 for GFS and ECMWF User guide V8.1 Contains important bugfixes!
Potential errors in output data, use V8.1!
Thanks to Caroline Forster for this version!
FLEXPART V6.2 User guide V6.2
FLEXPART V6.1 User guide V6.1
FLEXPART V6.0 User guide V6.0
FLEXPART V5.0 User guide V5.0
FLEXPART V4.0< User guide V4.0
FLEXPART V3.2 for GFS User guide V3.2

FLEXPART V3.1 User guide V3.1
FLEXPART V3.0b User guide V3.0

FLEXPART for input data from regional models (MM5, WRF)

Source code Description
FLEXPART for WRF Repository in Japan - many thanks to Saji N. Hameed for this development
FLEXPART for WRF large file (440 MB) - many thanks to Jerome Fast for this development
FLEXPART V6.2 for MM5 Thanks to Petra Seibert and Paul Skomorowski
FLEXPART V3.1 for MM5 Inaccurate coordinate transformation, use FLEXPART for MM5 version 6.2


Source code Manual
FLEXTRA V5.0 for GFS and ECMWF (GRIB2) - thanks to Stephan Henne for this version
FLEXTRA V3.0 for MM5

Additional libraries

In order to run FLEXTRA or FLEXPART, you need to have a GRIB decoding library installed on your computer.

The most recent version of the ECMWF's GRIB_API library (Version 1.6.1 or newer, currently tested up to version 1.9.5) is currently recommended for Flexpart 8.0+. The GRIB_API library is required to read in with current operational NCEP GFS model data which is diseminated in the compressed GRIB2 format. For input data in GRIB1 format, the GRIB_API is also recommended. For backward compatiblity, the EMOS GRIB library can still be used to work with GRIB1 data.

It is possible to download working GRIB versions from the UCAR website or from the ECMWF website. A good documentation of GRIB can be found here.

Additional FLEXPART documentation

Using the web-based products (PDF file) NEW
Documentation on the use of MM5 data for FLEXTRA/FLEXPART (HTML)
A FLEXPART tutorial in PowerPoint format written by Jimmy Leclair de Bellevue (PPT)

Routines for reading FLEXPART output files

Fortran routines for reading header and FLEXPART V8.0+ output files (Tarball) NEW - BUGFIX Nov 2010
pflexpart: Python routines for reading header and FLEXPART V8.0+ output files (HTML) NEW in Nov 2010

Routines for retrieval of FLEXTRA/FLEXPART input data from ECMWF

The ECMWF data retrieval routines are kindly provided by Leopold Haimberger, Gerhard Wotawa, and others.

Version 4.0 routines for ECMWF data retrieval NEW, allows to retrieve compressed ECMWF data in mixed GRIB1/GRIB2 coding
Version 2.1 routines for ECMWF data retrieval Includes important bugfixes
Version 2.0 routines for ECMWF data retrieval
Version 1.0 routines for ECMWF data retrieval

Description for retrieval of FLEXPART GFS input data

These description is kindly provided by Jooil Kim and Bob Dattore (NCAR)

Now there exists a well-managed source of archived windfields from NCEP for use with FLEXPART. Here are the instructions:

1. Go to website:

2. Log in with your ucar account, or create one for free.

3. Click the "Data Access" tab -> "Internet Download" link -> "Request a Subset with Format Conversion" link. This opens up a window for choosing a customized subset of the CFSR data.

4. Choose your time period, and select "FLEXPART Model Input - 6-hour Forecasts" under the Parameter presets. When done, push the "Continue" button on the bottom of the page.

5. On the next window, look for the "Type of Product" menu and select "all available", then push the "Click Here" button to update. Doing this will give you the 0hr analysis and 1hr~6hr forecast winds. When done, push the "Submit Request" button.

6. You will receive an e-mail from UCAR when the data is ready. Follow instructions on the e-mail regarding ways to download the data.

7. Note: The 0hr analysis data (labeled "pgbhnl") do not have some of the surface variables like 2 meter temperature and 10 meter winds, and so they do not work with FLEXPART. Use the 6hr forecast files instead.


Descriptions of FLEXPART in the scientific literature are:

Stohl, A., C. Forster, A. Frank, P. Seibert, and G. Wotawa (2005): Technical Note : The Lagrangian particle dispersion model FLEXPART version 6.2. Atmos. Chem. Phys. 5, 2461-2474.

Stohl, A., and D. J. Thomson (1999): A density correction for Lagrangian particle dispersion models. Bound.-Layer Met. 90, 155-167.

Stohl, A., M. Hittenberger, and G. Wotawa (1998): Validation of the Lagrangian particle dispersion model FLEXPART against large scale tracer experiments. Atmos. Environ. 32, 4245-4264.

Various specific components of the models that were implemented more recently can be found in other publications (see Andreas Stohl's publication list and the FLEXTRA and FLEXPART publication lists).

Descriptions of FLEXTRA in the scientific literature are:

Stohl, A., G. Wotawa, P. Seibert, and H. Kromp-Kolb (1995): Interpolation errors in wind fields as a function of spatial and temporal resolution and their impact on different types of kinematic trajectories. J. Appl. Meteor. 34, 2149-2165.

Stohl, A., and P. Seibert (1998): Accuracy of trajectories as determined from the conservation of meteorological tracers. Q. J. Roy. Met. Soc. 124, 1465-1484.

Andreas Stohl's Home Page

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