.. _flexpart_plotting_flux_fields:

FLEXPART - Plotting flux fields
###############################
 
For preparations and running the FLEXPART simulation needed for this tutorial :ref:`click here ... <flexpart_forward_simulation>`

.. note::

  To start this tutorial please enter folder 'forward'.

Inspecting the FLEXPART GRIB file
*********************************

Before seeing the macro code to generate the plot we inspect the file itself we want to plot. 
Double-click on the 'flux_s001.grib' GRIB icon' in folder 'result_fwd' to start up the **Grib Examiner**. 
We can see that our GRIB file contains various flux fields. 
We can find out further details about the parameters by setting the **Dump mode** to *Namespace* and **Namespace** to *Parameter* in the examiner:

.. image:: /_static/flexpart_plotting_flux_fields/image2017-10-25_13-34-50.png

Generating the plot
*******************

The macro to visualise the flux fields on a given level is 'plot_flux.mv'.

In the macro first we define the level (8000 m) and the parameter ("feflux" = eastward flux) we want to plot. 
Then we call :func:`flexpart_filter` to extract the data.
  
.. code-block:: python
  
  dIn="result_fwd/"
  inFile=dIn  & "conc_s001.grib"
  lev=8000
  par="feflux"  
  
  #Read fields on the given height level
  g=flexpart_filter(source: inFile,
                    param: par,
                    levType: "hl", 
                    level: lev)
  
Next, we define the contouring. 
The "feflux" fields have the units of "kg m**-2 s**-1" but with the current value range "ng m**-2 s**-1" units would better fit for contouring. To achieve this we simply multiply the "feflux" fieldset with 1012:   
  
.. code-block:: python
  
  g=g*1E12
  
The contour definition itself goes like this:   
  
.. code-block:: python
  
  #The contour levels
  cont_list=[1,10,50,100,150,200,250,500,750,1000,2000,4000]  
  
  #Define contour shading
  flux_shade = mcont(
      legend                          :   "on",
      contour                         :   "off",  
      contour_level_selection_type    :   "level_list",
      contour_level_list              :   cont_list,
      contour_label                   :   "off",
      contour_shade                   :   "on",
      contour_shade_method            :   "area_fill",
      contour_shade_max_level_colour  :   "red",
      contour_shade_min_level_colour  :   "RGB(0.14,0.37,0.86)",
      contour_shade_colour_direction  :   "clockwise",    
      contour_method                  :   "linear"
      )
  
Next, we build the title with :func:`flexpart_build_title`. 
Please note that we need to explicitly specify the plotting units! 
  
.. code-block:: python
  
  title=flexpart_build_title(data: g,
      fontsize: 0.3, 
      units: "ng m**-2 s**-1")  
  
Finally we define the map view:  
  
.. code-block:: python
  
  #Define coastlines
  coast_grey = mcoast(
      map_coastline_thickness         :   2,
      map_coastline_land_shade        :   "on",
      map_coastline_land_shade_colour :   "grey",
      map_coastline_sea_shade         :   "on",
      map_coastline_sea_shade_colour  :   "RGB(0.89,0.89,0.89)",
      map_boundaries                  :   "on",
      map_boundaries_colour           :   "black",
      map_grid_latitude_increment     :   5,
      map_grid_longitude_increment    :   5
      )  
 
  #Define geo view
  view = geoview(
      map_area_definition :   "corners",
      area                :   [40,-25,66,9],
      coastlines          : coast_grey
      )
  
and generate the plot:  
  
.. code-block:: python
  
  plot(view,g,flux_shade,title)
  
Having run the macro we will get a plot like this (after navigating to step 39h):

.. image:: /_static/flexpart_plotting_flux_fields/image2017-10-25_13-25-40.png