The 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. Note that in addition to data retrieval, this module also has post-processing options such as Grid and Area, for regridding and sub-area extraction respectively; these use the same interpolation routines as the standard ECMWF MARS client.
From Macro/Python the icon can be called as
The MARS Retrieval Editor
It is beyond the scope of this documentation to provide explanation to the MARS Retrieval parameters and in general about MARS. Instead, it is strongly recommended to consult the MARS user documentation, especially the MARS keywords documentation to find out details about how to define MARS retrievals.
The MARS Catalogue
The MARS Catalogue is an extremely useful site where you can browse the contents of the full archive. It has an additional feature that could help define MARS Retrievals in Metview (both as an icon and Macro/Python code).
This is how it works: 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.
Clicking on this link and selecting the Metview macro tab you will see the Macro code defining the retrieval. This can be straight used in Macro and can also help editing the MARS Retrieval icon.