Multi-layer plotting #1580
Description
What problem does your feature request solve?
It would be useful to have functionality for multi-variable plotting, e.g. to overlay variableA on variableB. Example output below, illustrating overplotting of temperature (base layer) and precipitation (masked overlay) with MSLP (contours):
Functionality should be merged with #1483, offering flexibility of number and type of plotting 'layers'.
Describe the solution you'd like
In workflow, envisage support via new section of Diagnostics tab (i.e. rather than to be run by default as a surface (2D) field type), where users could specify 'base_variable', 'masked_variable', 'contour_variable' etc. Other aspects of plotting would pick up standard CSET defaults.
This change requires new recipe(s), and updates to plotting routines (or new ones) to support multi-layer plotting.
Describe alternatives you've considered
I have prototyped already to create above examples, so think this is feasible and desirable.
Functionality based on some of the functionality supported in other analysis tools, including ukep_plot (where overplotting contours etc relatively hard-coded and activated/deactivated only by commenting/uncommenting relevant code blocks!).
This change could also evolve into support for different variables, or plotting treatment between land/sea points etc (or any other filtering/masking). Nice illustrations of these were generated at WCRP K-Scale hackathon (will insert link here).