...

ODB stands for Observational DataBase and is developed at ECMWF to manage very large observational data volumes through the ECMWF IFS/4DVAR-system. The data structure of an ODB database can be seen as a table of variables called columns. Right-click examine the ODB Database icon AMSUA.odb to see a list of the variables in the data. The Data tab provides access to the actual data itself. ODB data can be filtered using ODB/SQL queries. The supplied ODB Filter icon contains an ODB/SQL query to retrieve certain columns of data. Edit it - note that this pre-prepared icon is using the AMSUA.odb icon as its data input. Look at the ODB Query field to get an idea of what data will be filtered. Now close the editor and examine the icon to see the filtered subset of data it has produced. The ODB Visualiser icon tb_plot tells Metview which columns of data to use for the visualisation; visualise it and apply the symb_colours icon to obtain a nice plot.

There is a dedicated tutorial for handling ODB data in Metview on the Tutorials page.

Extra Work

Optimisations to file writing

...

• in fact, it could be done with a single write() function if we just build up a string representing the whole file with newline characters between lines
• if writing many many lines, there is another syntax which avoids multiple file open and close operations:

  • Code Block
    fh = file('output.txt') # open a file handle for i = 1 to 100 do write(fh, 'Line ' & i & newline) end for fh = 0 # close the file handle

ODB

Visualise different columns of data in the supplied ODB file.

See if you can write a macro which extracts lat, lon and value columns into vectors and creates a new geopoints variable from the data.