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DRAFT


How to prepare FLEXPART input data?


How to run FLEXPART?

To run a FLEXPART simulation you need to use the FLEXPART Run icon.The simulation itself requires:

  • input meteorological fields
    These can be generated for FLEXPART using the FLEXPART Prepare icon or with an external application.
  • the FLEXPART executable
    At ECMWF it is centrally installed and does not need to be specified for FLEXPART Run. For a custom-build executable or at other sites please follow the instructions in FLEXPART setup.
  • some FLEXPART resources
    FLEXPART needs a set of files to carry out a simulation: IGBP_int1.dat, OH_7lev_agl.dat, surfdata.t, surfdepo.t. At ECMWF these are centrally installed and do not need to be specified for FLEXPART Run. At other sites please follow the instructions here.
  • setting the SPECIES to be released
    The species we can use in a FLEXPART simulation must be defined by a set of ASCII files. See details about their usage here. 
  • specifying the releases
  • defining the run conditions
  • the path to the output files
    Metview runs FLEXPART in a temporary folder then converts the results and copies them into this folder. FLEXPART outputs can be large so take it into account when selecting this path.

How to specify the FLEXPART executable?



How to define the releases?

A release is defined with the FLEXPART Release icon. In our example the release is defined with iconshappens at a point between 1651 and 9000 m. The emitted mass is 100 kg.

The macro code,

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
	)


The location of the FLEXPART executable and that of some other files/directories have to be specified for Metview. These locations can be defined either through a set of Metview environment variables or via parameters in the FLEXPART Run icon (these latter take precedence). The table below summarises what actually is needed to set for Metview.

 

The FLEXPART executableNeed to be built from FLEXPART sourceMV_FLEXPART_EXE_PATHUser Exe Path

The directory containing the following files:

  • IGBP_int1.dat
  • OH_7lev_agl.dat
  • surfdata.t
  • surfdepo.t

These files are distributed in the FLEXPART source inside folder option

MV_FLEXPART_RESOURCES_PATHUser Resources Path
The directory containing the species

A set of species are distributed in the FLEXPART source inside folder option/SPECIES

MV_FLEXPART_SPECIES_PATHUser Species Path

 


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.

You will create some icons yourself, but some are supplied 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 flexta_tutorial folder. You will work in this folder so 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:

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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