This tutorial explains how to convert ECMWF GRIB data into VAPOR format and how to visualise the resulting data in VAPOR.
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Please note that this tutorial requires Metview version 4.4.4 or later. Also for users outside ECMWF the Metview VAPOR interface should be properly set up as described here. |
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Preparations
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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. You should now (after a few seconds) see a vapor_tutorial folder which contains the solutions and also some additional icons required by these exercises. You should work in the thethis vapor_tutorial folder so open it up now. You will see the following contents:
VAPOR Basics
VAPOR stands for Visualization and Analysis Platform for Ocean, Atmosphere, and Solar Researchers. It is a software system providing an interactive 3D visualization environment. The home of the software is https://www.vapor.ucar.edu.
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- pl.grib: contains z, t, r, u and v on pressure levels
- pl_surf.grib: contains z, 2t ,10u and 10v on surface
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Please note that both these files were retrieved from MARS by using the 'ret_pl' and 'ret_pl_surf' MARS retrieval icons in the solutions folder.
Running Vapor Prepare
Create a VAPOR Prepare icon (use right-click in the desktop when no icons are selected and use the New icon ... menu).
Rename it 'vapor_pl' and open up its editor.
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This exercise demonstrate how to use model level ECMWF GRIB data with VAPOR when elevation available/can be derived. We will work with fields on the same low resolution grid over Europe as we used for the pressure levels.
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The GRIB data is already in its place. In your folder you will find the three GRIB files you need to use for this exercise:
- ml.grib: contains q, t, u and v on model levels 137-60
- ml_lnsp.grib: contains lnsp on the bottommost model level (level 137)
- ml_surf.grib: contains z, 2t ,10u and 10v on surface).
Please note that both these files were retrieved from MARS by using the 'ret_ml', 'ret_ml_lnsp' and 'ret_ml_surf' MARS retrieval icons in the solutions folder.
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Please note that upper level geopotential (z) is not available in the input files because it is not archived in MARS for model levels. However, VAPOR Prepare can derive it if tempreature (t), specific humidity (q) and logarithm of surface pressure (lnsp) are available . We has to ensure that these fields were present in our data. (it is the case for our input data). |
Running Vapor Prepare
Create a VAPOR Prepare icon. Rename it 'vapor_ml' and open up its editor.
First, ensure that Vapor Input Mode is set to Icon then drop your three Mars Retrieval icons into the Vapor Input Data field.
Second, Then you need to define the list of GRIB parameters you want to see in VAPOR.
| Vapor 2d Params | z/2t/10u/10v |
| Vapor 3d Params | t/u/v/q |
Third, set the The vertical coordinate system has to be set carefully:
| Vapor Vertical Grid Type | Layered |
| Vapor Elevation Param | z |
| Vapor Bottom Coordinate | 0 |
| Vapor Top Coordinate | 16000 |
Here we you set the vertical grid type to layered and defined geopotential (z) as the parameter holding the elevation of the vertical layers (model levels). We also specified the vertical coordinate range (in metres) that VAPOR will display for this data.
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Although geopotential (z) is not available on model levels in the input data VAPOR Prepare computes it automatically if tempreature (t), specific humidity (q) and logarithm of surface pressure (lnsp) are available. Geopotential is then gets converted into metres units and renamed to ELEVATION. |
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| Vapor Vdf Name | tut_ml |
| Vapor Output Path | your_path_on_the_filesystem |
| Vapor Reuse Vdf | On |
Now save your VAPOR Prepare icon then right click Execute to run the conversion. The icon will first turn orange then green when the conversion finishes.
To visualise the VAPOR data generated please follow the instructions here.
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Right click Visualise your VAPOR Prepare icon to start up VAPOR. You will see this window popping up:
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We can load a pre-installed map image to get a better geographical reference for the domain we are looking at. Open the Image tab and load 'BigBlueMarble.tiff' by using the Select Installed Image button. Then tick Instance: 1, tick Apply to Terrain and set Z to 0. The scene has now changed like this:
The VAPOR session file
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The current scene settings can be saved into a VAPOR session file (with a .vss suffix) by using the File → Save Session (As) menu. Then next time we start up VAPOR the saved session files can be loaded to initialise the scene with the saved settings. |
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