Technical note: The Lagrangian particle dispersion model FLEXPART version 6.2

A. Stohl, C. Forster, A. Frank, P. Seibert, G. Wotawa
2005 Atmospheric Chemistry and Physics  
The Lagrangian particle dispersion model FLEXPART was originally (about 8 years ago) designed for calculating the long-range and mesoscale dispersion of air pollutants from point sources, such as after an accident in a nuclear power plant. In the meantime FLEXPART has evolved into a comprehensive tool for atmospheric transport modeling 5 and analysis. Its application fields were extended from air pollution studies to other topics where atmospheric transport plays a role (e.g., exchange between
more » ... , exchange between the stratosphere and troposphere, or the global water cycle). It has evolved into a true community model that is now being used by at least 25 groups from 14 different countries and is seeing both operational and research applications. A user manual has been kept actual over 10 the years and was distributed over an internet page along with the model's source code. However, so far there was no citeable description of FLEXPART. In this note we provide a description of FLEXPART's latest version (6.2). 20 of a computational grid and have, in principle, infinitesimally small resolution. The basis for current atmospheric particle models was laid by Thomson (1987) , who stated the criteria that must be fulfilled in order for a model to be theoretically correct. A monograph on the theory of stochastic Lagrangian models was published by Rodean (1996) and another good review was written by Wilson and Sawford (1996). 25 The theory of modeling dispersion backward in time with Lagrangian particle models 4740 ACPD 5, 2005 EGU was developed by Flesch et al. (1995) and Seibert and Frank (2004) . Reviews of the more practical aspects of particle modeling were provided by Zannetti (1992) and Uliasz (1994) . This note describes FLEXPART, a Lagrangian particle dispersion model that simulates the long-range and mesoscale transport, diffusion, dry and wet deposition, and 20 2003). The most recent version described here is 6.2, which saw corrections to the numerics in the convection scheme, the addition of a domain-filling option, and the possibility to use output nests. FLEXPART is coded following the Fortran 77 standard and tested with several compilers (gnu, Absoft, Portland Group) under a number of operating systems (Linux, So-25 laris, etc.). The code is carefully documented and optimized for run-time performance. No attempts have been made to parallelize the code because the model is strictly linear and, therefore, it is most effective to partition problems such that they run on single processors and to combine the results if needed. 5, 2005 EGU FLEXPART's source code and a manual are freely available from the internet page ∼ andreas/flextra+flexpart.html. According to a recent user survey, at least 25 groups from 14 countries are currently using FLEXPART. The version of FLEXPART described here is based on model level data of the numerical weather prediction model of the European Centre for Medium-Range Weather Fore-5 casts (ECMWF). Other users have developed FLEXPART versions using input data from a suite of different global (e.g., from the National Centers of Environmental Prediction) and meso-scale (e.g., MM5) models, some of which are available from the FLEXPART website but are not described here. 4741 ACPD Input data and grid definitions 10 FLEXPART is an off-line model that uses meteorological fields (analyses or forecasts) in Gridded Binary (GRIB) format from the ECMWF numerical weather prediction model (ECMWF, 1995) on a latitude/longitude grid and on native ECMWF model levels as input. The data can be retrieved from the ECMWF archives using a pre-processor that is also available from the FLEXPART website but not described here. The GRIB 15 decoding software is not provided with FLEXPART but is publicly available (see links on the FLEXPART website). The data can be global or only cover a limited area. Furthermore, higher-resolution domains can be nested into a mother domain. The file includepar contains all relevant FLEXPART parameter settings, both physical constants and maximum field dimensions. As the memory required by 20
doi:10.5194/acp-5-2461-2005 fatcat:pgbgoxrv75bvhoo6ka4367qqe4