Adds light rain diagnostic for spatial plots, difference and timeseries

[David Flack (daflack)]

Includes recipes, and plumbing into the workflow.

Fixes #1853

Contribution checklist

Aim to have all relevant checks ticked off before merging. See the developer's guide for more detail.

• Documentation has been updated to reflect change.
• New code has tests, and affected old tests have been updated.
• All tests and CI checks pass.
• Ensured the pull request title is descriptive.
• Ensure rose-suite.conf.example has been updated if new diagnostic added.
• Conda lock files have been updated if dependencies have changed.
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• Marked the PR as ready to review.

[github-actions]

[David Flack (daflack)]

Example of light rain presence and rainfall field for same time showing only light rain is selected

example of spatial difference:

example of timeseries:

[David Flack (daflack)]

As two masks are multiplied together we lose the name of the diagnostic in the cube we are plotting. To get a name will necessitate a new operator that can add the name as meta-data to the cube. The operator will just call cube.rename, with an input of the name of the variable and the cube.

Thus a question for reviewers: should this operator be included in this PR or as a different PR? I'm happy either way.

[ukmo-huw-lewis]

Happy to pick up review on this one if useful and others requested don't get there first.

First look through proposed changes and example output looks sensible and to be working, and nice use of masking to capture upper and lower thresholds.

On the question re. extra PR for the naming operator, I suggest you capture this within this current PR, as a function of the multiply operator being introduced. Rather than create a new operator however, suggest you consider any options for preserving or adjusting names more directly in the multiplier code. There is arguably some precedent for this with the difference operator in misc.py. Maybe the difference here is we're showing "mask x mask", but want it labelled as "rain present diagnostic"...... Interested to see proposed solution.

[David Flack (daflack)]

Added in naming convention into the multiplication operator and an extra operator for renaming for situations like "mask x mask" when they have a specific meaning like "light rain", and put this into the recipe. I kept the naming convection "mask_for" to allow the relevant mask colourscales for the mask and mask differences to be plotted. Examples for spatial plot and spatial plot difference below. Only difference for timeseries is axis name and the fixed axis between 0 and 1.

ukmo-huw-lewis now ready for full review

[ukmo-huw-lewis]

Changes look good overall, and update to plotting output example look great.

Suggest to tidy up and respond to comments before happy to take another look and close this one out.

[David Flack (daflack)]

ukmo-huw-lewis comments addressed/responded to, back to you.

[ukmo-huw-lewis]

Thanks for responses. Happy to approve.

Will merge.