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The GRIB Filter icon is used to filter GRIB data from either a MARS Retrieval icon carries out the retrieval of data from the ECMWF archive. It is therefore the crucial, and necessarily the most used Metview icon. Data retrieved by this icon is used as input to most other Metview icons (though they may also use data from other icons). The Metview MARS Retrieval icon essentially represents a translation of the MARS (Meteorological Archival and Retrieval System) language into a Metview icon editor listing or a GRIB file icon. You can then obtain just the field(s) you want from a large request/file containing a wide variety of other field(s).

You may ask yourself, why filter a MARS Retrieval instead of retrieving from the database exactly the data you want, thus avoiding the extra filtering step? The usefulness depends on what you want to do :

It may be more efficient to retrieve (and save) a large chunk of data with a single MARS Retrieval and then filter fractions of the large dataset with GRIB Filter. Remember that the large chunk of data, once retrieved is cached (or you may have saved it) and further access to it via GRIB Filter is much faster than making many separate individual MARS Retrievals.

Info

From Macro/Python the icon can be called as retrieveread().



The

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GRIB Filter Editor

It is beyond With the scope exception of the this documentation to provide explanations to the MARS Retrieval parameters and in general about MARS.  Instead, it is strongly recommended to consult the MARS user documentation and especially the MARS keywords documentation to find out details about the MARS keywords..

The MARS Catalogue

The MARS Catalogue is an extremely useful site where you can browse the contents of the full archive. When you reach the page in the catalogue where the actual parameters, steps and levels to be retrieved appear you will find a View the MARS Request link.

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Clicking on this link and selecting the Metview macro tab you will see the Macro code defining the retrieval.

a few parameters which specify the data to be filtered, all other parameters found in the GRIB Filter editor can also be found in the  MARS Retrieval editor.

Source

Specifies the GRIB file path and name. Type the full file path and name.

Data

Drop a MARS Retrieval or a GRIB file icon inside this icon field. Note that you should specify either Source or Data, not both, otherwise the process will fail.

Order

Specifies whether you want to sort the files you have filtered (Sorted) or to obtain them in the order they are on the original file (As Is). The sorting is the same as that carried out by MARS on retrieving data (date, time, forecast step, level, parameter), hence this has no effect if you are filtering a MARS request (or a GRIB file containing the result of a single MARS retrieval).Image Removed