The Lagrangian particle dispersion model FLEXPART Jimmy LECLAIR DE BELLEVUE Presentation to UKZN training session - 09 Nov 2006 3-D visualization of an.

The Lagrangian particle The Lagrangian particle dispersiondispersion

model FLEXPARTmodel FLEXPART

Jimmy LECLAIR DE BELLEVUEJimmy LECLAIR DE BELLEVUE

Presentation to UKZN training Presentation to UKZN training session - 09 Nov 2006session - 09 Nov 2006

3-D visualization of an intrusion of stratospheric air into the troposphere, resulting from a FLEXPART simulation. The domain shown covers Europe, and the uppermost level is at 13 km

ContentContent

ReferencesReferences IntroductionIntroduction What is good in FLEXPART ?What is good in FLEXPART ? System requirements & versionsSystem requirements & versions Summary of the available versionsSummary of the available versions SetupSetup UseUse Important aspects of the physicsImportant aspects of the physics Case studies of stratospheric to tropospheric Case studies of stratospheric to tropospheric

exchanges : Examplesexchanges : Examples Take-Home messageTake-Home message

ReferencesReferences

http://zardoz.nilu.no/~andreas/flextra+flexpart.htmlhttp://zardoz.nilu.no/~andreas/flextra+flexpart.html

Descriptions of FLEXPART in the scientific literature are:Descriptions of FLEXPART in the scientific literature are:

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

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

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

IntroductionIntroduction FLEXPART is an atmospheric trajectory and a particle dispersion model, FLEXPART is an atmospheric trajectory and a particle dispersion model,

respectively, that are used by a growing user community.respectively, that are used by a growing user community.

A recent user survey resulted in 34 groups from 17 countries who have confirmed A recent user survey resulted in 34 groups from 17 countries who have confirmed to actively use one of the models for a variety of research purposes.to actively use one of the models for a variety of research purposes.

Applications of the models cover topics like transport of radionuclides after nuclear Applications of the models cover topics like transport of radionuclides after nuclear accidents, pollution transport, greenhouse gas cycles, stratosphere-troposphere accidents, pollution transport, greenhouse gas cycles, stratosphere-troposphere exchange, water cycle research, and others.exchange, water cycle research, and others.

Development supervised by Andreas Stohl and mainly by people from Development supervised by Andreas Stohl and mainly by people from Norwegian Institute of Air Research, Kjeller, NorwayNorwegian Institute of Air Research, Kjeller, Norway Institute of Meteorology, University of Natural Resources and Applied Life Institute of Meteorology, University of Natural Resources and Applied Life

Sciences, Vienna, AustriaSciences, Vienna, Austria Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty

Organization, Vienna, AustriaOrganization, Vienna, Austria

FLEXPART is being developed continuously !FLEXPART is being developed continuously !

http://zardoz.nilu.no/~andreas/

IntroductionIntroduction

Lagrangian particle models compute trajectories of a large number of so-called particles (not necessarily representing real particles, but infinitesimally small air parcels) to describe the transport and diffusion of tracers in the atmosphere.

The main advantage of Lagrangian models is that, unlike in Eulerian models, there is no numerical diffusion.

FLEXPART is a Lagrangian particle dispersion model that simulates the long-range and mesoscale transport, diffusion, dry and wet deposition, and radioactive decay of tracers released from point, line, area or volume sources.

FLEXPART can be used forward in time to simulate the dispersion of tracers from their sources, or backward in time to determine potential source contributions for given receptors.

What is good in FLEXPART ?What is good in FLEXPART ? FLEXPART was evaluated using data from three large-scale tracer experiments, namely theFLEXPART was evaluated using data from three large-scale tracer experiments, namely the

Cross-Appalachian Tracer Experiment (CAPTEX),Cross-Appalachian Tracer Experiment (CAPTEX), Across North America Tracer Experiment (ANATEX)Across North America Tracer Experiment (ANATEX) European Tracer Experiment (ETEX), European Tracer Experiment (ETEX),

comprising a total of 40 releases.comprising a total of 40 releases.

The results of this validation study are described in Stohl et al. (1998), but in summary one can The results of this validation study are described in Stohl et al. (1998), but in summary one can say that FLEXPART seems to belong to the better dispersion models currently available.say that FLEXPART seems to belong to the better dispersion models currently available.

This is also supported by the ATMES-II model intercomparison study, where FLEXPART This is also supported by the ATMES-II model intercomparison study, where FLEXPART scored among the best models.scored among the best models.

It requires only a short computation time, has a finer spatial resolution and does not suffer It requires only a short computation time, has a finer spatial resolution and does not suffer numerical diffusion compared to chemistry transport models (CTMs). numerical diffusion compared to chemistry transport models (CTMs).

It is a compromise between simple trajectory calculations and complex CTMs that makes best It is a compromise between simple trajectory calculations and complex CTMs that makes best use of available computer hardware.use of available computer hardware.

The model is freeware and can be downloadedThe model is freeware and can be downloaded

System requirements & System requirements & versionsversions

FLEXPART, written in FORTRAN 77, is largely platform independent. It FLEXPART, written in FORTRAN 77, is largely platform independent. It currently runs on SUN, SGI, HP, Compaq Alpha and LINUX workstations.currently runs on SUN, SGI, HP, Compaq Alpha and LINUX workstations.

(also on IBM, done in Reunion Island University)(also on IBM, done in Reunion Island University)

FLEXPART can be driven with meteorological input data from a variety of FLEXPART can be driven with meteorological input data from a variety of global and regional models, most commonly from the global and regional models, most commonly from the EuropeanEuropean Centre for Medium Range Centre for Medium Range WeatherWeather ForecastsForecasts (ECMWF) (ECMWF). .

It runs where a Fortran 77 compiler and a It runs where a Fortran 77 compiler and a GRIB GRIB decodingdecoding software software to to read ECMWF input data.read ECMWF input data.

The memory requirements depend on the spatial domain of your input The memory requirements depend on the spatial domain of your input fields and the number of particles you want to use. fields and the number of particles you want to use.

The ECMWF version of the model is considered as the reference version, The ECMWF version of the model is considered as the reference version, but a new GFS version of FLEXPART is available (porting of the ECMWF but a new GFS version of FLEXPART is available (porting of the ECMWF version to use GFS data). version to use GFS data).

Summary of the available Summary of the available versionsversions

FLEXPART V6.2 (based on ECMWF input data)FLEXPART V6.2 (based on ECMWF input data)

FLEXPART V6.4 for GFS (Contact Caroline Forster : [email protected])FLEXPART V6.4 for GFS (Contact Caroline Forster : [email protected]) On 24 April 2002 the NCEP AVN model was renamed to the GFS (Global Forecast System) On 24 April 2002 the NCEP AVN model was renamed to the GFS (Global Forecast System) GFS Products : GFS Products : http://www.nco.ncep.noaa.gov/pmb/products/gfs/http://www.nco.ncep.noaa.gov/pmb/products/gfs/

FLEXPART V3.1 for MM5FLEXPART V3.1 for MM5 FLEXPART for WRF (Contact Jerome Fast : FLEXPART for WRF (Contact Jerome Fast : [email protected])@pnl.gov)

The Weather Research and Forecasting (WRF) Model is a next-generation mesocale numerical weather The Weather Research and Forecasting (WRF) Model is a next-generation mesocale numerical weather prediction system designed to serve both operational forecasting and atmospheric research needs. prediction system designed to serve both operational forecasting and atmospheric research needs.

The effort to develop WRF has been a collaborative partnership, principally among the National Center for The effort to develop WRF has been a collaborative partnership, principally among the National Center for Atmospheric Research (NCAR), the National Oceanic and Atmospheric Administration (the National Centers Atmospheric Research (NCAR), the National Oceanic and Atmospheric Administration (the National Centers for Environmental Prediction (NCEP) and the Forecast Systems Laboratory (FSL), the Air Force Weather for Environmental Prediction (NCEP) and the Forecast Systems Laboratory (FSL), the Air Force Weather Agency (AFWA), the Naval Research Laboratory, Oklahoma University, and the Federal Aviation Agency (AFWA), the Naval Research Laboratory, Oklahoma University, and the Federal Aviation Administration (FAA). Administration (FAA).

WRF homepage : WRF homepage : http://www.wrf-model.org/index.phphttp://www.wrf-model.org/index.php

Routines for the retrieval of FLEXPART input data from ECMWFRoutines for the retrieval of FLEXPART input data from ECMWF Tools to analyze the output : NCAR Graphics programs and statistical programs availableTools to analyze the output : NCAR Graphics programs and statistical programs available

Setup of FLEXPARTSetup of FLEXPART

The pathnames file A file pathnames must exist in the directory where FLEXPART is started. It states the

pathnames of input and output files: /home/as/FLEXPART50/options/ /volc/as/contrace/modelresults/forward/ /volc/windcontrace/ /volc/windcontrace/AVAILABLE /volc/nested/ /volc/nested/AVAILABLE ============================================ Line 1: path where control files "COMMAND" and "RELEASES" are available Line 2: name of directory where output files are generated Line 3: path where meteorological fields are available (mother grid) Line 4: full filename of "AVAILABLE"-file (mother grid) Subsequent lines: Line 2n+3: path where meteorological fields are available (nested grid n) Line 2n+4: full filename of "AVAILABLE"-file (nested grid n)

The file IncludeparThe file Includepar

The file includepar contains all relevant FLEXPART parameter settings, both The file includepar contains all relevant FLEXPART parameter settings, both physical constants and maximum field dimensions. physical constants and maximum field dimensions.

As the memory required by FLEXPART is determined by the various field As the memory required by FLEXPART is determined by the various field dimensions, it is recommended that they are adjusted to actual needs before dimensions, it is recommended that they are adjusted to actual needs before compilation.compilation.

To avoid « segmentation fault », change the variables size :To avoid « segmentation fault », change the variables size :

maxpart(2000)maxpart(2000) maxpoint (1)maxpoint (1) maxrand(2000)maxrand(2000)

Compilation : make –f makefileCompilation : make –f makefile

Use of FLEXPARTUse of FLEXPART

The AVAILABLE file The directory where the meteorological input data are stored, here called windfields

(/volc/windcontrace/ in the above example pathnames file), contains grib-code files containing the ECMWF data. All meteorological fields must have the same structure, i.e. the same computational domain and the same resolution. An example listing of this directory is given below.

The file names of the grib-code files and their validation dates and times (in UTC) must be listed in the file AVAILABLE. While it is practical to have this file reside in the same directory as the wind fields, this is no necessity and it can also be located elsewhere, as its file name is also given in the pathnames file.

DATE TIME FILENAME SPECIFICATIONS YYYYMMDD HHMISS ________ ______ __________ __________ 20011028 000000 EN01102800 ON DISC 20011028 030000 EN01102803 ON DISC 20011028 060000 EN01102806 ON DISC 20011028 090000 EN01102809 ON DISC 20011028 120000 EN01102812 ON DISC

Files in directory options

The files in directory options are used to specify the model run.

Very important are :

COMMAND RELEASES OUTGRID

File COMMAND :

The most important file is the COMMAND file which specifies (1) the simulation direction (either forward or backward), (2) the start and (3) the end time of the simulation, (4) the frequency Tc of the model output, (5) the averaging time Tc of model output, etc …

Files in directory options

File RELEASES :File RELEASES :

RELEASES defines the release specifications :

The beginning and the ending time of the release, Geographical coordinates of the lower left and upper right corners of

the release location, type of vertical coordinate (above ground level, or above sea level), lower level and upper level of source box, the number of particles to be used

The particles are released from random locations within a four-dimensional box extending from the lower to the upper level above a rectangle (on a lat/lon grid) defined by the geographical coordinates, and between the release’s start and end.

Files in directory options

The file OUTGRID specifies the output grid, Change if necessary

EXECUTION OF FLEXPART :

./FLEXPART

rather quick, a few dizaines of particles during five days : < 10 minutes

Important aspects of the Important aspects of the physics in FLEXPARTphysics in FLEXPART

Mesoscale velocity fluctuations :

Mesoscale motions are neither resolved by the ECMWF data nor covered by the turbulence

parameterization.

This unresolved spectral interval needs to be taken into account at least in an approximate way, since mesoscale motions can significantly accelerate the growth of a dispersing plume (Gupta et al., 1997).

For this, a similar method as Maryon (1998), namely to solve an independent Langevin equation for the mesoscale wind velocity fluctuations (“meandering” in Maryon’s terms).

This empirical approach does not describe actual mesoscale phenomena, but it is similar to the ensemble methods used to assess trajectory accuracy (Kahl , 1996; Baumann and Stohl, 1997; Stohl, 1998).

Important aspects of the physics in FLEXPARTImportant aspects of the physics in FLEXPART

Moist Convection :

An important transport mechanism are the updrafts in convective clouds.

They occur in conjunction with downdrafts within the clouds and compensating subsidence in the cloudfree surroundings.

These convective transports are grid-scale in the vertical, but sub-grid scale in the horizontal, and are not represented by the ECMWF vertical velocity.

To represent convective transport in a particle dispersion model, it is necessary to redistribute particles in the entire vertical column.

For FLEXPART the convective parameterization scheme chosen is from Emanuel and Zivkovic-Rothman (1999), as it relies on the gridscale temperature and humidity fields and calculates a displacement matrix providing the necessary mass flux information for the particle redistribution.

The convective parameterization is switched on using lconvection in file COMMAND.

It’s computation time scales to the square of the number of vertical model levels and may account for up to 70% of FLEXPART’s computation time using current 60-level ECMWF data.

Important aspects of the physics in FLEXPARTImportant aspects of the physics in FLEXPART Clustered Clustered plume trajectories : In a recent paper, Stohl et al. (2002) proposed a method to condense the complex and large FLEXPART output using a cluster analysis (Dorling et al., 1992).

The idea behind this is to cluster, at every output time, the positions of all particles originating from a release point, and write out only clustered particle positions.

This option can be activated by setting iout to 4 or 5 in file COMMAND.

The number of clusters can be set with the parameter ncluster in file includepar.

Output : Output : Condensed particle output using the clustering algorithm is written to the formatted file trajectories.txt. Condensed particle output using the clustering algorithm is written to the formatted file trajectories.txt.

Information on the release points (coordinates, release start and end, number of particles) is written by subroutine Information on the release points (coordinates, release start and end, number of particles) is written by subroutine openouttraj.f to the beginning of file trajectories.txt. openouttraj.f to the beginning of file trajectories.txt.

Subsequently, plumetraj.f writes out a time sequence of the clustering results for each release point : release Subsequently, plumetraj.f writes out a time sequence of the clustering results for each release point : release point number, time in seconds elapsed since the middle of the release interval, plume centroid position point number, time in seconds elapsed since the middle of the release interval, plume centroid position coordinates, and then for each cluster the cluster centroid position, the fraction of particles belonging to the coordinates, and then for each cluster the cluster centroid position, the fraction of particles belonging to the cluster, and the root-mean-square distance of cluster member particles from the cluster centroid.cluster, and the root-mean-square distance of cluster member particles from the cluster centroid.

Case studies of tratospheric Case studies of tratospheric to tropospheric exchanges : to tropospheric exchanges : ExamplesExamples

IRENE

REUNION

Clustered plume trajectories

15/02/02 12TU 9.5-10.5km

19/02/02 12TU 8-9km

Not clustered plume trajectories

Take-home messageTake-home message Thanks for your attention !Thanks for your attention !

You will read the following later :You will read the following later : Access and use of FLEXPART shall impose the following obligations on the user. Access and use of FLEXPART shall impose the following obligations on the user.

The user is granted the right, without any fee or cost, to use, copy, modify, alter, enhance and The user is granted the right, without any fee or cost, to use, copy, modify, alter, enhance and distribute FLEXPART, and any derivative works thereof, and its supporting documentation for any distribute FLEXPART, and any derivative works thereof, and its supporting documentation for any purpose whatsoever, except commercial sales, provided that this entire notice appears in all copies of purpose whatsoever, except commercial sales, provided that this entire notice appears in all copies of the software, derivative works and supporting documentation.the software, derivative works and supporting documentation.

This software is provided by the University of Munich "as is" and any express or implied warranties, This software is provided by the University of Munich "as is" and any express or implied warranties, including but not limited to, the implied warranties of merchantability and fitness for a particular including but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall the University of Munich be liable for any special, indirect or purpose are disclaimed. In no event shall the University of Munich be liable for any special, indirect or consequential damages or any damages whatsoever, including but not limited to claims associated consequential damages or any damages whatsoever, including but not limited to claims associated with the loss of data or profits, which may result from an action in contract, negligence or other tortious with the loss of data or profits, which may result from an action in contract, negligence or other tortious claim that arises out of or in connection with the access, use or performance of FLEXPART.claim that arises out of or in connection with the access, use or performance of FLEXPART.

Schematic of a Schematic of a lagrangian modellagrangian model