What is FLEXPART?
FLEXPART is a Lagrangian particle dispersion model developed and used by a large international scientific community. It can be driven by meteorological input data from a variety of global and regional models including ECMWF analyses and forecasts.
The home of the software is https://www.flexpart.eu/.
How to use FLEXPART with Metview?
Metview provides a high level interface to prepare input data for FLEXPART from ECMWF's MARS archive (via the FLEXPART Prepare icon),
perform a FLEXPART integration (via the FLEXPART Run icon)
and visualise the resulting output files. For the visualisation the gridded outputs in FLEXPART's custom binary format are converted to GRIB.
The interface was written for version 9.02 of FLEXPART.
Further details
There is a tutorial available on the use of FLEXPART with Metview. It explains both the data preparation steps and the basics of the visualisation.