ENH: Corrections to gradient pblh schemes, updates to examples

[jrobrien91]

What changed

Gradient PBLH schemes have been corrected to reflect literature standards, mainly defining the PBLH as the "sharpest negative gradient". Previously, the scheme was coded as the "first negative gradient".

Additional maximum height constraints have been added to both schemes for consistency with other ACT PBLH schemes.

Examples recreated to use the miniMPL from the SGP-REAL activity, for the 30 March IOP. This date was selected as it is completely cloud free REAL-IOP. This also corrects ACT's PBLH examples for wavelet and gradient schemes, which previously used a cloud capped SGP ceilometer example.

Why

During analysis for the SGP-REAL activity, it was noted the gradient schemes should be corrected to reflect literature standards.

Additionally, examples should use realistic examples and not instances were the retrieval is not valid for, such as cloud-capped PBLs.

Issues closed

N/A

Validation

Mark each item as done or N/A. Add one short evidence line for each item.

• I ran pre-commit or ruff

• I ran tests and/or added tests

AI usage & manual verification

If AI tools were used, complete this section.

• AI used: Yes
• Model/tooling: Claude Sonnet 5
• Tasks delegated to AI: Evaluate the Gradient PBLH schemes for consistency with literature and amongst ACT PBLH retrievals. Claude also wrote the test for the maximum height on the gradient PBLH estiamte.
• Manual verification performed: Tested and rebuilt the PBLH examples using the miniMPL.

Impact note (optional):

• breaking behavior -- this will adjust the PBLH estimates for the gradient method for end users. Also should note the PBLH schemes require range in meters, hence the addition of the km to m correction within the examples.