[2304] Adjust eval for precipitations

[vhertel]

Description

Summary

Generalizes the eval/plotting pipeline with a focus on precipitation. Variable plotting options can now be matched by glob, colormaps can be discrete/custom, and per-stream/channel colorbar scaling supports log/symlog for skewed distributions.

Changes

• Glob-based variable selection: plotting options can be keyed by exact channel name or a glob pattern (e.g. tp_*, v_*).
• Custom/discrete colormaps: added a colors option that builds discrete colormaps to match references like RAINA precipitation.
• Per-stream/channel colorbar scaling: replaced the boolean log_colorbar flag with a colorbar_scale option. linear is the default and fallback. log is for single-sign skewed distributions like tp, but requires vmin > 0, otherwise it warns and falls back to linear. symlog handles double-sign variables like v and u (if distribution is skewed) as well as non-linear bias plots.

Examples

(1) RAINA cmap and log bias

  IMERG_ANEMOI:
    "tp_*":
      colorbar_scale: "log"
      levels: [0.0001, 0.0005, 0.001, 0.002, 0.005, 0.01, 0.02]
      colors:
        - "none"
        - "#BEDAE5"
        - "#80B5CC"
        - "#5691B3"
        - "#4B6E9C"
        - "#424B83"
        - "#45596D"
        - "#5B9E4C"

Target

Bias

(2) Continuous and log cmap

  IMERG_ANEMOI:
    "tp_*":
      colorbar_scale: "log"
      vmin: 1.0e-6
      colormap: "Blues"

Target

(3) ERA5 example with discrete cmap

  ERA5:
    "q_*":
      levels: [0.0001, 0.0005, 0.001, 0.002, 0.005, 0.015, 0.03]

Target

Issue Number

Closes #2304

Checklist before asking for review

• I have performed a self-review of my code
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  • I have added unit tests, if relevant
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