Adding hurs (realtive humidity) derivation script

[malininae]

Hi folks,

Following the April 2024 monthly meeting, I'm adding the relative humidity derivation (hurs). Before being able to open a real PR, I would need to add filtering in case the hurs_cb.data >100%. Also need to write test. Will do it before the workshop.

This PR is related to #2254 .

[bouweandela]

Suggested change

	cubes_difference = iris.analysis.maths.subtract(tas_cube, tdps_cube)
	cubes_difference = tas_cube - tdps_cube

Would this also work? Did you read the section on cube maths in the iris documentation?

[malininae]

Thanks, so when I was trying it with simple tas_cube-tdps_cube the issue was that I was running out of memory, while it wasn't a case with subtract. I will test it again with the time diagnostic and will let you know.

[bouweandela]

That would be surprising because it should do the same thing, i.e. the minus operator on an Iris cube is implemented using the exact same function:
https://github.com/SciTools/iris/blob/c5e0353da11c263656c6c77e5e56eafefcede077/lib/iris/cube.py#L3968

[bouweandela]

would need to add filtering in case the hurs_cb.data >100%

This could probably be done with code like this:

import dask.array as da
hurs_cb.data = da.ma.where(hurs_cb.core_data() > 100., hurs_cb.core_data(), 100.)

[bouweandela]

If you would like a quicker response in the future, it usually helps if you tag people so they get a notification, e.g. @bouweandela

[codecov]

Codecov Report

Attention: Patch coverage is 52.17391% with 11 lines in your changes missing coverage. Please review.

Project coverage is 94.89%. Comparing base (bd617f5) to head (5380c5f).

Files with missing lines	Patch %	Lines
esmvalcore/preprocessor/_derive/hurs.py	52.17%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2397      +/-   ##
==========================================
- Coverage   94.96%   94.89%   -0.07%     
==========================================
  Files         253      254       +1     
  Lines       14701    14724      +23     
==========================================
+ Hits        13961    13973      +12     
- Misses        740      751      +11     

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