Due to the nature of the data, the macro language provides little in the way of functions to process observations - you can only merge and/or plot them.
If you need to do more, you have to convert them to geopoints using the obsfilter() request. .
observations ( observations & observations )observations merge ( observations,observations )
Merges two sets of observations.
observations obsfilter ( definition )geopoints obsfilter ( definition )
The obsfilter() function is a Metview request, i.e. corresponds to a Metview icon available from the User Interface - Observation Filter . It accepts BUFR input, filters out part of that input (optional) and returns BUFR data (default) or geopoints (if user so specifies) in one of three geopoints formats - see Geopoints.
The input is a definition containing a named list of values, corresponding to the contents of the Observation Filter editor contents. Remember you need only specify the parameters which you want to change from their default values.