What is GRIB?
GRIB is the WMO's format for binary gridded data. The Metview GRIB interface is based on ecCodes and can handle both GRIB edition 1 and edition 2 seamlessly.
How to use Metview with GRIB?
GRIB files are represented by this icon in the user interface:
Examining GRIB contents
The contents of a GRIB file can be inspected with the GRIB Examiner, which can be either started up from user interface (right-click examine on the icon) or from the command line using the following command:
Visualisation on maps
GRIB (with the exception of spherical harmonics fields) can be directly visualised in Metview on a map view. In the user interface just right-click visualise on the icon to get a plot with the default settings. GRIB map plots can be further customised with the Contouring or Wind Plotting icons for scalar fields or vector fields, respectively.
Visualisation on other views
On top of the map-based visualisation we can also generate the following plot types from GRIB data:
- vertical cross sections (see Cross Section Data and Cross Section View)
- zonal and meridional averages (see Average Data and Average View)
- Hovmoeller diagrams (see Hovmoeller Data and Hovmoeller View).
It is also possible to extract vertical profiles (see Vertical Profile Data and Vertical Profile View) and time series.
The Thermo Data icon can prepare thermodynamic profiles which then can be visualised in a tephigram, skew-t or in emagram using a Thermo View.
Filtering and interpolation
The GRIB Filter icon provides the means to select a subset of fields from a GRIB file. It (and the MARS Retrieval icon) also contains some parameters, such as Grid, which allow for interpolation to a new grid.
Data processing
There are quite a few icons available in Metview to process GRIB data. These include the icons mentioned above and the following other icons:
- Percentile
- Relative Humidity
- Rotational or Divergent Wind
- Potential Temperature
- Simple Formula
- Spectra
- Velocity Potential or Stream Function
Metview's script interface provides access to all these icons and also offers a rich set of functions and operators to work with GRIB data (see Script Language Support below).
Retrieval from MARS
If Metview has access to ECMWF's MARS archive, GRIB data can be retrieved via the Mars Retrieval icon. At ECMWF MARS access is set up on all computer systems, while outside ECMWF the MARS Web API could be used in Metview (see the setup instructions here).
Script language support
Metview provides full support for GRIB from its Macro and Python interfaces. In script GRIB data is represented as a fieldset, which can be imagined as a list of GRIB messages. Fieldset handling probably Metview's richest and most powerful interface. The full list of available functions and operators on fieldsets can be found on the Fieldset Functions and Thermodynamic functions pages.
Tutorials
There is no dedicated tutorial for GRIB but the bulk of the Data analysis and visualisation using Metview online course is dealing with visualisation and processing of GRIB data. There is also the ECMWF New Users Metview Tutorial which provides an excellent introduction to Metview and GRIB handling.
FAQ
In Metview's FAQ page a whole section is devoted to GRIB-related questions.
Gallery
Most of the Gallery examples are related to GRIB data. Actually, all the plots shown on this page were taken from the Gallery (clicking on them leading to the actual code).