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Now, if you run this macro you should see a Display Window popping up showing both groups of trajectories using the default FLEXTRA visualisation.   Remarks

Tip

When we worked with the FLEXTRA Visualiser icon we specified the index of the trajectory group to be visualised. This approach is working in macro as well. E.g. in our macro we could have written the code for volcano Stromboli as:

Code Block
plot_Srtromboli=flextra_visualiser(
 	flextra_data: flx,
 	flextra_group_index: 2
 )

Data Access in Macro

In this example we will see how to access metadata and data from a FLEXTRA output file containing multiple trajectory groups.

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All the required fields, with one exception, can be retrieved from ECMWF's MARS archive. The only exception is the vertical velocity because FLEXTRA needs the following field for its computations:

∂p∂η 
Mathinline
\dot \eta \frac{\partial \eta}{\partial p}
The problem with this product is that only is archived in MARS and the full product needs to be computed during the data preparation process.

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Right-click and execute to start the data preparations again. This time your icon turns green almost immediately indicating that actually no data retrieval and processing happened. The reason for it is that we set parameter Flextra Reuse Input to 'On'. In this case Metview checks the existence of the data to be generated and if the data is already in place no new data is retrieved. The same happens with the AVAILABLE file.
 

Info

If parameter Flextra Reuse Input is set to 'On' Metview confirms the existence of a GRIB file by using the file name and a set of GRIB API keys from the first message in the file. This is the list of the keys that are checked:

  • date, time, stepRange
  • gridType
  • iDirectionIncrement, jDirectionIncrement
  • latitudeOfFirstGridPoint, latitudeOfLastGridPoint
  • longitudeOfFirstGridPoint, longitudeOfLastGridPoint

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