A case study
In this case study will run FLEXPART to simulate the imaginary eruption of the Icelandic volcano Eyjafjallajökull.
Preparations
First start Metview; at ECMWF, the command to use is metview
(see Metview at ECMWF for details of Metview versions). You should see the main Metview desktop popping up.
The icons you will work with are already prepared for you - please download the following file:
and save it in your $HOME/metview
directory. You should see it appear on your main Metview desktop, from where you can right-click on it, then choose execute to extract the files.
Alternatively, if at ECMWF then you can copy it like this from the command line:
cp -R /home/graphics/cgx/tutorials/flexpart_tutorial ~/metview
You should now (after a few seconds) see a flexpart_tutorial folder. Please open it up.
The input data
The input data is already prepared for you and is located in folder 'Data'. You will find a FLEXPART Prepare icon that was used to generate the data in folder 'Prepare'. The corresponding macro code can also be found there.
You do not need to run the data preparation. However, if you wish to do so please note that it requires MARS access and you must set the Output Path parameter accordingly.
Running a forward simulation
Enter folder 'fwd'.
We will run FLEXPART to simulate the release of SO2 from the Icelandic volcano Eyjafjallajökull.
The simulation is defined via the 'fwd_conc' FLEXPART Run and the 'rel_volcano' FLEXPART Release icons, respectively. Both these are encompassed in the 'fw_cond.mv' Macro. For simplicity will use this macro to show the simulation in detail.
First we define the release like this:
rel_volcano = flexpart_release( name : "REL 1", starting_date : 0, starting_time : 15, ending_date : 2, ending_time : 12, area : [63.63,-19.6,63.63,-19.6], top_level : 9000, bottom_level : 1651, particle_count : 10000, masses : 100 )
This says that the release will happen over a 45 h period between heights 1651 and 10000 m at the location of the volcano and we will release 100 kg worth of particles.
Please note that
- the species is not defined here (will be defined in
flexpart_run()
) - we used dates relative to the starting date of the simulation (see also in
flexpart_run()
)
The actual simulation is carried out by calling flexpart_run()
:
#Run flexpart (asynchronous call!) r = flexpart_run( output_path : "result_fwd_conc", input_path : "../data", starting_date : 20120517, starting_time : 12, ending_date : 20120519, ending_time : 12, output_field_type: "concentration", output_flux : "on", output_trajectory : "on", output_area : [40,-25,66,10], output_grid : [0.25,0.25], output_levels : [500,1000,2000,3000,4000,5000,7500,10000,15000], release_species : 8, receptors : "on", receptor_names : ["rec1","rec2"], receptor_latitudes : [60,56.9], receptor_longitudes : [6.43,-3.5], releases : rel_volcano ) print(r)
Here we defined the simulation period and the output grid as well. We also told FLEXPART to generate gridded concentration fields on output. We also asked for plume trajectories and deposition data at the specified receptor locations.
Please note that the actual species that will be released is defined as an integer number (for details about using the species see here).
If we run this macro (or alternatively right-click execute
the FLEXPART Run icon) the results (after a minute or so) will be available in folder 'result_fw_conc' . The computations were actually taken place in a temporary folder then metview copied the results here. If we open this older we will see two files there:
- cons_s001.grib is GRIB file containing the gridded concentration fields.
- tr_r1.csv is CSV file containing the plume trajectories
Please note that these are not the original outputs form FLEXTRA but were converted formats more suitable for use in Metview. For details about the FLEXPART outputs please click here.
Visualising gridded fields
Since the output GRIB files cannot be handled by Metview's standard Grib Filter icon because (due to the local GRIB definitions we use). Therefore a set of Metview Macro Library Functions were developed to deal with the FLEXPART grib files. Please look into the visualisation macros to see how to use them. The most important Metview Macro Library Functions are as follows:
|
|
|
Forward simultaions
Fields
Trajecories
receprotros
volume fill
fluxes
cross section
time-height diagram
total column
age class
backward simulation
residence time
fluxes
trajecory