Release Notes
=============

v2.0.0b1
--------

This is the first beta for the v2.0 release line. It is intended for early
users who want the new ECHAM/RRTMGP workflow, composable physics API, and
pluggable dynamical-core interface before the stable v2.0.0 tag.

Install the beta explicitly:

.. code-block:: console

   $ pip install "jcm==2.0.0b1"

Because ``2.0.0b1`` is a Python pre-release, normal ``pip install --upgrade
jcm`` users will continue to receive the latest stable release unless they opt
in with ``--pre`` or an exact version pin.

Highlights
^^^^^^^^^^

- Added the :class:`jcm.dycore.base.DynamicalCore` protocol and moved Dinosaur
  behind the shipped :class:`jcm.dycore.dinosaur.DinosaurDycore` backend.
- Refreshed the v2 documentation around dycore ownership, operator-split
  physics, composable physics, and the ECHAM target configuration.
- Made ECHAM the beta target for climate-quality integrations, especially
  ``physics=echam-rrtmgp grid=echam_t63_l47_hybrid``.
- Added persistent checkpoint/resume support for long and preemptible runs.
- Added ozone climatology forcing for ECHAM-RRTMGP.
- Consolidated shared physical constants behind
  :mod:`jcm.constants`, with runtime overrides via
  :func:`jcm.constants.set_constants` before model construction.
- Stabilized ECHAM cloud, convection, vertical diffusion, gravity-wave,
  aerosol, and surface-process wiring for the T63L47 beta target.
- Updated the Python package version to the canonical PEP 440 pre-release
  string ``2.0.0b1``.

Beta Fixes
^^^^^^^^^^

- ``echam_physics(radiation_scheme="rrtmgp")`` now configures the enclosing
  ``ComposablePhysics.band_config`` for RRTMGP bands, matching the Hydra
  runner path and avoiding broadband aerosol optics in Python-created RRTMGP
  compositions.
- Example notebooks were checked for v2 API drift; the ECHAM demo now uses
  ``predictions.to_xarray()``, ``Model(coords=..., terrain=...)``, and
  ``Parameters.float_zeros()``.

Known Beta Caveats
^^^^^^^^^^^^^^^^^^

- The pluggable dycore interface is present, but the shipped production backend
  remains Dinosaur. The Hydra CLI currently selects Dinosaur explicitly.
- Column-vectorized ECHAM physics still assumes a two-dimensional horizontal
  layout. Non-lat/lon dycores need an adapter or flattening step before using
  the shipped column physics packages.
- The beta is intended for named early users and API feedback. Pin the exact
  beta version in user environments and update deliberately between beta tags.