FLEXPART - Plotting flux fields

For preparations and running the FLEXPART simulation needed for this tutorial click here ...

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:

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 flexpart_filter() to extract the data.

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:

g=g*1E12

The contour definition itself goes like this:

#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 flexpart_build_title(). Please note that we need to explicitly specify the plotting units!

title=flexpart_build_title(data: g,
    fontsize: 0.3, 
    units: "ng m**-2 s**-1")  

Finally we define the map view:

#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:

plot(view,g,flux_shade,title)

Having run the macro we will get a plot like this (after navigating to step 39h):