EAMxx: add log-linear interpolation option to VerticalRemapper and FieldAtPressureLevel diagnostic

[bartgol]

Allows to perform interpolation w.r.t. the log of the pressure coordinate.

[non-BFB] Only for streams that used vertical remapping (via remapper or pressure-level diag).

---

This PR replaces #8183 and depends on #8375, so it may get rebased while we wait for that PR to be integrated.

[Copilot]

Pull request overview

This PR adds a log-linear vertical interpolation option (interpolating in
log-pressure space) to EAMxx vertical remapping and the FieldAtPressureLevel
diagnostic, and wires the option through IO stream configuration and selected
data-interpolation call sites.

Changes:

• Extend VerticalRemapper with an interpolation type (linear vs log-linear)
  and log-transform support for pressure coordinate fields.
• Thread a vert_interpolation_type stream parameter through Scorpio output and
  create_diagnostic, enabling log-linear pressure-level diagnostics.
• Update unit/integration tests and multi-process output configs to preserve
  existing behavior by explicitly selecting linear where needed.

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
components/eamxx/tests/multi-process/physics_only/shoc_p3_nudging/output_remapped.yaml	Pins stream vertical interpolation to linear for test stability.
components/eamxx/tests/multi-process/dynamics_physics/mam/homme_shoc_cld_spa_p3_rrtmgp_mam4_wetscav/output.yaml	Pins stream vertical interpolation to linear.
components/eamxx/tests/multi-process/dynamics_physics/mam/homme_shoc_cld_p3_mam_optics_rrtmgp/output.yaml	Pins stream vertical interpolation to linear.
components/eamxx/tests/multi-process/dynamics_physics/mam/homme_shoc_cld_mam_aci_p3_mam_optics_rrtmgp_mam_drydep/output.yaml	Pins stream vertical interpolation to linear.
components/eamxx/tests/multi-process/dynamics_physics/homme_shoc_cld_spa_p3_rrtmgp/output.yaml	Pins stream vertical interpolation to linear.
components/eamxx/tests/multi-process/dynamics_physics/homme_shoc_cld_spa_p3_rrtmgp_pg2_dp/output.yaml	Pins stream vertical interpolation to linear.
components/eamxx/tests/multi-process/dynamics_physics/homme_shoc_cld_spa_p3_rrtmgp_128levels/output.yaml	Pins stream vertical interpolation to linear.
components/eamxx/tests/multi-process/dynamics_physics/homme_shoc_cld_p3_rrtmgp_pg2/output.yaml	Pins stream vertical interpolation to linear.
components/eamxx/src/share/remap/vertical_remapper.hpp	Adds InterpType, log-pressure helper, and refactors pressure/coord storage by vertical tag.
components/eamxx/src/share/remap/vertical_remapper.cpp	Implements log-linear coordinate handling, tag-based LinInterp setup, and per-tag remap dispatch.
components/eamxx/src/share/remap/tests/vertical_remapper_tests.cpp	Updates pressure setup API usage and adds a log-linear remapper equivalence test.
components/eamxx/src/share/io/tests/io_remap_test.cpp	Adds a log-linear vertical remap integration path and adjusts numeric comparisons.
components/eamxx/src/share/io/scorpio_output.hpp	Stores per-stream vert_interpolation_type.
components/eamxx/src/share/io/scorpio_output.cpp	Reads vert_interpolation_type, configures VerticalRemapper and forwards to diagnostics creation.
components/eamxx/src/share/io/eamxx_io_utils.hpp	Extends create_diagnostic with vert_interp_type parameter.
components/eamxx/src/share/io/eamxx_io_utils.cpp	Forwards vert_interpolation_type into FieldAtPressureLevel params.
components/eamxx/src/share/diagnostics/tests/field_at_pressure_level_tests.cpp	Pins diagnostic interpolation to linear for existing test assumptions.
components/eamxx/src/share/diagnostics/field_at_pressure_level.hpp	Adds members to support log-linear interpolation.
components/eamxx/src/share/diagnostics/field_at_pressure_level.cpp	Implements log-linear interpolation branch for pressure-level diagnostic.
components/eamxx/src/share/algorithm/eamxx_data_interpolation.hpp	Adds an interpolation-type string to vertical remap configuration.
components/eamxx/src/share/algorithm/eamxx_data_interpolation.cpp	Creates VerticalRemapper with the requested interpolation type and updates pressure setup calls.
components/eamxx/src/physics/spc/eamxx_spc_process_interface.cpp	Reads optional vert_interpolation_type and forwards to DataInterpolation.
components/eamxx/src/physics/spa/eamxx_spa_process_interface.cpp	Reads optional vert_interpolation_type and forwards to DataInterpolation.
components/eamxx/src/physics/mam/readfiles/vertical_remapper_mam4.hpp	Removes obsolete set_target_pressure override from the MAM4 remapper interface.
components/eamxx/src/physics/mam/readfiles/vertical_remapper_mam4.cpp	Updates MAM4 remapper to the new pressure storage scheme (but currently has correctness issues).

[Copilot]

Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated 3 comments.

[bartgol]

OK, I think this is now ready for a review, since the 3 v1 diffs are expected. @crterai , you can also do a quick run to check if the output does look as expected. Recall that you don't need to do anything to get log-linear interpolation, as it is now the default. If you want to revert back to linear, you need to add vert_interpolation_type: linear at the top-level of your YAML file.

One thing to notice: the FieldAtPressureLevel diagnostic uses the same v interp type that the whole stream uses. This has a couple of implications:

1. Even if no vertical remapper is used in the stream, in order to move away from log-linear interp for the blah_at_XhPa diags, one has to set vert_interpolation_type: linear in the yaml file, which seems a bit counterintuitive
2. Given that the diag uses the vert interp set at the yaml file top level, we cannot mix linear and log-linear interpolation for 2+ FieldAtPressureLevel diagnostics

I believe the implications are mild, and we can live with that. Still, tagging other diags folks that may have an opinion: @mahf708 @jeff-cohere @AaronDonahue .