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In this exercise we will perform a backward simulation to compute the residence time of the particles reaching Inverness in Scotland. |
Running a backward simulation
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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- time_s001.grib is a GRIB file containing the gridded residence time field
Plotting residence times
Step 1 - Residence time
In this step we will plot the residence time for a given level.
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 'time_s001.grib' GRIB icon' in folder 'result_bwd' to start up the Grib Examiner. We can see that this file contains the "fprt" (=Residence time) fields we want to visualise. We can find out further details about this parameter by setting the Dump mode to Namespace and Namespace to Parameter:
Generating the plot
The macro to visualise the residence time on a given level is 'plot_time.mv'.
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Having run the macro we will get a plot like this (after navigating to step -27h):
Step 2 - Total residence time in a layer
In this step we will plot the total residence time summed up for the bottom 500m layer.
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Having run the macro we will get a plot like this (after navigating to step -27h):
Step 3 - Total residence time in the whole atmospheric column
Macro 'plot_time_total.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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Having run the macro we will get a plot like this (after navigating to step -27h):
Step 4 - Total residence time in a layer for the whole period
In this step we will plot the total residence time summed up for the whole period for the bottom 500m layer.
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Having run the macro we will get a plot like this:
Step 5 - Total residence time in the whole atmospheric column for the whole period
In this step we will plot the total residence time summed up for the whole period for the whole atmospheric column.
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