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Preparations

First start Metview; at ECMWF, the command to use is metview4_new (see Metview at ECMWF for details of Metview versions). You should see the main Metview desktop which looks something like Figure 1 (except that the tabbed area at the bottom will not be open) popping up.

You will create some icons yourself, but some are supplied for you - please download the following file:

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 main Metview desktop, not the solutions the vapor_tutorial folder.

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VAPOR

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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.

VAPOR vertical grid types

It is crucially important to understand the vertical coordinate types of the input data VAPOR can use. Here we discuss only the two types that the Metview VAPOR interface supports. These are as follows: layered and regular.  

•  For layered grids VAPOR expects a parameter specifying the elevation of each 3D level in the input data. This is typically the case for  pressure or model level (η levels) data with height or geopotential available (or it can be computed).
• For regular grids the 3D levels are supposed to be equidistant (in the user coordinate space). This type can be used when the data is available on equidistant hight levels.

The situation when pressure or model level data is present without height information is somewhat special. The grid in this case is not layered but can be regarded as regular in its own coordinate space (pressure or model levels) letting the z axis simply represent pressure or model levels in the 3D scene rendered in VAPOR.

Pressure level data with elevation

This exercise demonstrate how to use pressure level ECMWF GRIB data with VAPOR when elevation (as geopotential) is available. We will work with fields from yesterday's forecast on a low resolution grid over Europe.

Getting the GRIB data

The GRIB data is already in its place. In your folder you will find the two GRIB files pl.grib (for pressure levels) and pl_surf.grib (for surface) you need to use for this exercise.

Please note that both these files were retrieved from MARS.

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

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