...
First start Metview; at ECMWF, the command to use is metview (see Metview at ECMWF for details of Metview versions). You should see the main Metview desktop popping up.Next get a copy of the icons needed for the tutorial. If you are
You will create some icons yourself, but some are supplied for you - please download the following file:
| Panel | ||
|---|---|---|
| ||
Alternatively, if at ECMWF then you can copy |
...
it like this from the command line |
...
: |
| Code Block |
|---|
|
...
| Panel | ||
|---|---|---|
| ||
and save it in your $HOME/metview directory. You should see it appear on your main Metview desktop, from where you can right-click on it, then choose execute to extract the files.Last find the newly created . You should now (after a few seconds) see a flexta_tutorial folder which contains the solutions and also some additional icons required by these exercises. You will work in the flextra_tutorial folder in the Metview desktop and so open it (double-click to open)up. You should see the following contents:
...
About FLEXTRA
What is FLEXTRA?
FLEXTRA is an atmospheric trajectory model used by a large user community. It can be driven by meteorological input data from a variety of global and regional models including ECMWF analyses and forecasts.
...
| Warning |
|---|
Please note that FLEXTRA is not an ECMWF development. FLEXTRA is not distributed with Metview, but it has to be downloaded from the web site specified above and installed separately. It is installed at ECMWF though. |
About the Metview interface
Metview provides a high level interface to prepare input data for FLEXTRA, run FLEXTRA and visualise the resulting output files. The interface was developed and tested with version 5.0 of FLEXTRA, which is using GRIB API to handle GRIB2 fields.
...
In this exercise we will see how to compute trajectories with FLEXTRA in NORMAL run mode. In NORMAL mode we can generate a group of trajectories starting from the same point but at different times. Please open folder 'normal' inside folder 'flextra_tutorial' to start the work.
The FLEXTRA Run Icon
To compute trajectories with FLEXTRA we need to use the FLEXTRA Run icon (right-click in the desktop when no icons are selected and use the New icon ... menu).
...
With these settings we specified the trajectory type to be three-dimensional (see below for the list of IDs for trajectory types) and set the starting point to volcano Katla (on Iceland) with the height of 1512m.
Remarks
The format of parameters holding dates is yyyymmdd. Any dates having less than 8 digits are interpreted as relative dates. E.g, -1 = yesterday, 0 = today, 1 = tomorrow etc.
...
| Note | ||
|---|---|---|
| ||
Another problem with global GRIB2 input fields is that FLEXTRA interprets the longitude span of the domain either as 0-360 or 180-540 (!!!) degrees depending on the geometry settings in the GRIB headers. The actual range can be figured out from the header of the FLEXTRA output files. In both cases we need to guarantee that the starting point we specify is in the given coordinate range. Otherwise FLEXTRA fails with the following message:
In the first case it is trivial to ensure it, while in the second case we need to add 360 to the longitude to make FLEXTRA accept the starting point. |
Running FLEXTRA
Save your FLEXTRA Run icon (Apply) then right-click and execute to start the trajectory computations. Within a minute (it might take longer on your machine) the icon should turn green indicating that the run was successful and the results have been cached.
The FLEXTRA File icon
Our FLEXTRA run generated an ASCII file on output which is now represented by our FLEXTRA Run icon. Right-click and examine the icon to look to see its content. This action will start up a window showing the output generated by FLEXTRA. What you are looking at is a custom ASCII format describing the resulting trajectories and some metadata.
...
In this exercise we will visualise the trajectories that we computed in the previous chapter. We will work in folder 'normal' again.
The FLEXTRA Visualiser Icon
To visualise your FLEXTRA output you need to use a FLEXTRA Visualiser icon.
...