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

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rel_inv = flexpart_release(
	name			:	"INVERNESS",
	starting_date	:	1,
	starting_time	:	12,
	ending_date		:	2,
	ending_time		:	12,
	area			:   [57.44/-4.23/57.46/-4.21],
	top_level		:	500,
	bottom_level	:	0,
	particle_count	:	10000,
	masses			:	1
	)

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Here we defined both the input and output path paths and specified the simulation period, the output grid and levels as well. We also told FLEXPART to generate residence time fields on output.

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_bwd'. The computations actually took place in a temporary folder then Metview copied the results to the output folder. If we open this folder we will see one file heretwo files:

• time_s001.grib is a GRIB file containing the gridded residence time field
• log.txt is the logfile generated by FLEXPART

Plotting residence times

Step 1 - Residence time

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dIn="result_fwd/"
inFile=dIn  & "conctime_s001.grib"
lev=700
par="fprt"
 
#Read fields on the given height level
g=flexpart_filter(source: inFile,
                  param: par,
                  levType: "hl", 
                  level: lev)

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Macro 'plot_time_step3.mv' shows how to plot the total residence time for the whole atmospheric column. It goes exactly like Step 2 but we need to omit top_level and bottom_level in the flexpart_total_column() call:

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