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This tutorial explains how to use the FLEXPART Lagrangian dispersion model within Metview.

Requirements

Please note that this tutorial requires Metview version 5.0 or later.

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:

Download

flextra_tutorial.tar.gz

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 a volcano eruption by releasing of some SO2 from the Icelandic volcano Eyjafjallajökull.

The simulation is defined by the 'fwd_conc' FLEXPART Run icon and the 'rel_volcano' FLEXPART Release icon, respectively. Both these are encompassed in a single Macro called 'fw_cond.mv'. For simplicity will use this macro to examine the settings in detail. 

First we define the release like this:

rel_volcano = flexpart_release(
	name			:	"VOLCANO", 
	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			:	1000000
	)

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 1000 tons of material.

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:

mvl_flexpart_read_hl(inFile,par,lev,ts,ac)
  
# Function to get flexpart fields on height level
# params:
#   inFile: input file
#   par: parameter shortname
#   lev: level (-1 means all)
#   ts: step (-1 means all)
#   ac: ageclass (-1 means all)

mvl_flexpart_read_sfc(inFile,par,ts,ac)
  
# Function to get surface flexpart fields
# params:
#   inFile: input file
#   par: parameter shortname
#   ts: step (-1 means all)
#   ac: ageclass (-1 means all)

mvl_flexpart_total_column(inFile,ac)
  
# Function to compute the column-integrated density for concentration
# params:
#   inFile: input file
#   ac: ageclass (-1 means all)

 




Forward simultaions

Fields

Trajecories

receprotros

volume fill

fluxes

cross section

time-height diagram

total column

age class

backward simulation

residence time

fluxes

trajecory






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