This icon generates the gridded input data and the AVAILABLE file needed to run the FLEXTRA trajectory model. The input forecast or analysis fields are automatically retrieved from ECMWF's MARS archive. A tutorial on using FLEXTRA from within Metview is available from the Tutorials page. For help on editing icons, please see Editing Icons.
The macro language equivalent is flextra_prepare().
About FLEXTRA input data
The following is for information only - FLEXTRA Prepare handles these details internally.
FLEXTRA requires input fields on a regular latitude-longitude grid in GRIB format. The input data must contain four three-dimensional fields: the two horizontal wind components, vertical velocity and temperature. Two additional two-dimensional fields are needed as well: topography and surface pressure. The three-dimensional input data has to be available on ECMWF model (i.e. η) levels defined by a hybrid vertical coordinate system. An important restriction is that all the data fields used within a FLEXTRA run must have the same domain size, resolution, number of levels, etc.
All the required fields, with one exception, can be retrieved from ECMWF's MARS archive. The only exception is vertical velocity because FLEXTRA needs the following field for its computations: \( \dot \eta \frac{\partial \eta}{\partial p} \) Since only \( \dot \eta \) is archived in MARS the full product needs to be computed during the data preparation process (FLEXTRA Prepare does it for you).
FLEXTRA requires all the input GRIB files to be in the same folder using the following file naming convention: ENyymmddhh. In addition to the GRIBs FLEXTRA needs several parameter files as well. Most of these files are automatically generated by Metview in the background, so users do not need to create them. The only exception is the file called AVAILABLE because it can be optionally provided by the user.
The FLEXPART Run Editor
Flextra Prepare Mode
Specifies the data preparation mode. The possible values are: Forecast and Period.
In Forecast mode the selected steps of a given forecast can be used for data generation. If the mode is set to Period a period with a start and end date and constant time-step can be defined. In this case FLEXTRA Prepare tries to retrieve analysis fields from MARS whenever it is possible (for dates in the past) and uses forecast fields otherwise (for dates in the future).
Flextra Fc Mars Expver
The MARS experiment identifier of the forecast fields. The default value is 1 (operational forecast).
Flextra An Mars Expver
The MARS experiment identifier of the analysis fields. The default value is 1 (operational analysis).
Flextra Date
Specifies the run date of the forecast. Available when Flextra Prepare Mode is Forecast.
Flextra Time
Specifies the run time of the forecast . Available when Flextra Prepare Mode is Forecast.
Flextra Step
Specifies the forecast steps in hours. Here a list of values is given. Available when Flextra Prepare Mode is Forecast.
Flextra Period Start Date
Specifies the start date of the period. Available when Flextra Prepare Mode is Period.
Flextra Period Start Time
Specifies the start time of the period. Available when Flextra Prepare Mode is Period.
Flextra Period End Date
Specifies the end date of the period. Available when Flextra Prepare Mode is Period.
Flextra Period End Time
Specifies the end time of the period. Available when Flextra Prepare Mode is Period.
Flextra Period Step
Specifies the time step of the period in hours. The allowed values are as follows: 3 or 6. Available when Flextra Prepare Mode is Period.
Flextra Area
Specifies the area of the output grid in south/west/north/east format. The default value is -90/-180/90/180.
Flextra Grid
Specifies the resolution of the output grid in dx/dy format, where dx is the grid increment in east-west direction, while dy is the grid increment in north-south direction (both in units of degrees). The default value is: 1/1.
Flextra Top Level
Only data on and below this model level will be used to generate the FLEXTRA input fields. This level can be specified either as a model level or as a pressure value. In the latter case FLEXTRA Prepare will use the data retrieved for the first date to determine the topmost model level. The default value of this parameter is 1, which means that all the model levels will be used if Flextra Top Level Units is set to Model Levels.
Flextra Top Level Units
Specifies the units of the value of Flextra Top Level. The allowed values are Model Levels or hPa. The default value is Model Levels.
Flextra Reuse Input
If this parameter is set On FLEXTRA Prepare checks the existence of the data files to be generated and if they are already in place no new data is retrieved and processed. If it is Off all the fields are always retrieved and processed and the existing data files are overwritten. The same happens to the AVAILABLE file. The existence of a FLEXTRA input GRIB file is checked by using the file name and a set of GRIB API keys from the first message in the file. These keys are as follows: date, time, stepRange, gridType, iDirectionIncrement, jDirectionIncrement, latitudeOfFirstGridPoint, latitudeOfLastGridPoint, longitudeOfFirstGridPoint, longitudeOfLastGridPoint.
Flextra Output Path
Specifies the output directory (it has to be an absolute path) where the GRIB files and the AVAILABLE file will be generated. If this directory does not exist Metview will create it. The output GRIB files have the following naming convention: ENyymmddhh.
1. Simulation direction, 1 for forward, -1 for backward in time
2. Beginning date and time of simulation. Must be given in format
YYYYMMDD HHMISS, where YYYY is YEAR, MM is MONTH, DD is DAY, HH is HOUR,
MI is MINUTE and SS is SECOND. Current version utilizes UTC.
3. Ending date and time of simulation. Same format as 3.
4. Average concentrations are calculated every SSSSS seconds.
5. The average concentrations are time averages of SSSSS seconds
duration. If SSSSS is 0, instantaneous concentrations are outputted.
6. The concentrations are sampled every SSSSS seconds to calculate the time
average concentration. This period must be shorter than the averaging time.
7. Time constant for particle splitting. Particles are split into two
after SSSSS seconds, 2xSSSSS seconds, 4xSSSSS seconds, and so on.
8. All processes are synchronized with this time interval (lsynctime).
Therefore, all other time constants must be multiples of this value.
Output interval and time average of output must be at least twice lsynctime.
9. CTL must be >1 for time steps shorter than the Lagrangian time scale
If CTL<0, a purely random walk simulation is done
10.IFINE=Reduction factor for time step used for vertical wind
11.IOUT determines how the output shall be made: concentration
(ng/m3, Bq/m3), mixing ratio (pptv), or both, or plume trajectory mode,
or concentration + plume trajectory mode.
In plume trajectory mode, output is in the form of average trajectories.
12.IPOUT determines whether particle positions are outputted (in addition
to the gridded concentrations or mixing ratios) or not.
0=no output, 1 output every output interval, 2 only at end of the
simulation
13.Switch on/off subgridscale terrain parameterization (increase of
mixing heights due to subgridscale orographic variations)
14.Switch on/off the convection parameterization
15.Switch on/off the calculation of age spectra: if yes, the file AGECLASSES
must be available
16. If IPIN=1, a file "partposit_end" from a previous run must be available in
the output directory. Particle positions are read in and previous simulation
is continued. If IPIN=0, no particles from a previous run are used
17. IF IOUTPUTFOREACHRELEASE is set to 1, one output field for each location
in the RLEASE file is created. For backward calculation this should be
set to 1. For forward calculation both possibilities are applicable.
18. If IFLUX is set to 1, fluxes of each species through each of the output
boxes are calculated. Six fluxes, corresponding to northward, southward,
eastward, westward, upward and downward are calculated for each grid cell of
the output grid. The control surfaces are placed in the middle of each
output grid cell. If IFLUX is set to 0, no fluxes are determined.
19. If MDOMAINFILL is set to 1, the first box specified in file RELEASES is used
as the domain where domain-filling trajectory calculations are to be done.
Particles are initialized uniformly distributed (according to the air mass
distribution) in that domain at the beginning of the simulation, and are
created at the boundaries throughout the simulation period.
20. IND_SOURCE switches between different units for concentrations at the source
NOTE that in backward simulations the release of computational particles
takes place at the "receptor" and the sampling of particles at the "source".
1=mass units (for bwd-runs = concentration)
2=mass mixing ratio units
21. IND_RECEPTOR switches between different units for concentrations at the receptor
1=mass units (concentrations)
2=mass mixing ratio units
22. MQUASILAG indicates whether particles shall be numbered consecutively (1) or
with their release location number (0). The first option allows tracking of
individual particles using the partposit output files
23. NESTED_OUTPUT decides whether model output shall be made also for a nested
output field (normally with higher resolution)
24. LINIT_COND determines whether, for backward runs only, the sensitivity to initial
conditions shall be calculated and written to output files
0=no output, 1 or 2 determines in which units the initial conditions are provided.