VAPOR tutorial

This tutorial explains how to convert ECMWF GRIB data into VAPOR format and how to visualise the resulting data in VAPOR.

Pressure level data

In this exercise we will see how to use pressure level ECMWF GRIB data with VAPOR. We will work with fields from yesterday's forecast on a low resolution grid over Europe.

Retrieving the GRIB data

First, we retrieve our GRIB data from MARS. We need two MARS retrieval icons: one for the surface and one for the pressure levels.

Now create a MARS Retrieval icon for the surface fields. Rename it 'ret_surf', then apply the following settings:

Create another MARS Retrieval icon for the pressure level fields. Rename it 'ret_pl' and edit it in the following way:

Setting up Vapor Prepare

Having set up the retrievals we can focus on the conversion of the data into the VAPOR format.

Now, create a VAPOR Prepare icon. Rename it 'vapor_pl' and open up its editor.

First, we ensure that Vapor Input Mode is set to 'Icon' then drop the two Mars Retrieval icons into the Vapor Input Data field.

Second, we define the list of GRIB parameters we want to see in VAPOR.

Third, we set the vertical coordinate system:

We set the vertical grid type to 'Layered' and defined geopotential (z) as the parameter holding the elevation of the vertical layers (pressure levels).  Internally, VAPOR Prepare converts geopotential to metres and rename it ELEVATION (this is required by VAPOR). We also specified the vertical coordinate range (in metres) that VAPOR will display.

Last, we specify the name and location of the results of the conversion:

With these settings a VDF file called 'tut_pl.vdf' will be created in the directory you specified. All the other VAPOR data files will be placed into this directory into a subdirectory called 'tut_pl_data'. By setting Vapor Reuse Vdf to 'On' we told VAPOR Prepare not to run the conversion if a VDF file already exits in the target location.

Now save your VAPOR Prepare icon then right click Execute.

Running Vapor Prepare

Model level data

Retrieving the GRIB data

First, we need to retrieve our GRIB data from MARS. We need to create two MARS retrieval icons: one for the surface and one for the pressure levels.

Now create a MARS Retrieval icon for the surface fields. Rename it 'ret_surf', then apply the following settings:

Create another MARS Retrieval icon for the pressure level fields up to 100 hPa. Rename it 'ret_pl' and edit it in the following way:

Setting up Vapor Prepare

Having set up the retrievals we can focus on converting the data into the VAPOR format.

Now, create a VAPOR Prepare icon. Rename it 'vapor_pl' and open up its editor.

First, ensure that Vapor Input Mode is set to Icon then drop your two Mars Retrieval icons into the Vapor Input Data field.

Second, define the list of GRIB parameters you want to see in VAPOR.

Third, set the vertical coordinate system:

We set the vertical grid type to layered and defined geopotential (z) as the parameter holding the elevation of the vertical layers (pressure levels).  Internally, a VAPOR Prepare converts this parameter for metres units and rename it ELEVATION (this is required by VAPOR). We also specified the vertical coordinate range (in metres) VAPOR will display for this data.

Last, we specify  the name and location of the results of the conversion:

With these settings a VDF file called 'tut_pl.vdf' will be created in the directory you specified. All the other VAPOR data files will be placed into this directory into a subdirectory called 'tut_pl_data'. By setting Vapor Reuse Vdf to On we told VAPOR Prepare not to run the conversion if there is a VDF file already exists in the target location.

Now save your VAPOR Prepare icon.

Running Vapor Prepare