feat: add CosmoDownscaling diagnostic model (ERA5 -> COSMO-REA6/REA2)

CHANGELOG.md

@@ -30,6 +30,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   reflectivity, rain rate, and 1-hour accumulation (`OPERA`)
 - Added support for cumulative variables in ARCO data source
 - Added DLESyM-v0-ISCCP-ERA5 climate model
+- Added COSMO-REA downscaling diagnostic model (`CosmoDownscaling`) for
+  regression (mean) and diffusion downscaling of ERA5 to COSMO-REA6 (6 km) and
+  COSMO-REA2 (2.2 km), with movable sub-domain support via `set_domain`
 
 ### Changed
 

docs/conf.py

@@ -214,6 +214,12 @@ def linkcode_resolve(domain, info):
     "show_memory": False,
     "exclude_implicit_doc": {r"load_model", r"load_default_package"},
     "log_level": {"backreference_missing": "warning", "gallery_examples": "debug"},
+    # COSMO-REA weights are not yet publicly hosted, so this example raises without
+    # a local $COSMO_REA_PACKAGE. Whitelist it so the full gallery build does not
+    # fail; remove this entry once the package is hosted (load_default_package).
+    "expected_failing_examples": [
+        "../examples/03_downscaling/04_cosmo_rea_downscaling.py",
+    ],
 }
 
 # -- sphinx-badges configuration ----------------------------------------------

docs/modules/models_dx.rst

@@ -41,6 +41,7 @@ etc.
       CBottleTCGuidance
       CorrDiffCMIP6
       CorrDiffTaiwan
+      CosmoDownscaling
       ClimateNet
       DerivedRH
       DerivedRHDewpoint

docs/userguide/about/install.md

@@ -586,6 +586,26 @@ pip install earth2studio[corrdiff]
 uv add earth2studio --extra corrdiff
 ```
 
+:::
+::::
+:::::
+:::::{tab-item} COSMO-REA Downscaling
+Notes: Additional dependencies for the `CosmoDownscaling` model.
+
+::::{tab-set}
+:::{tab-item} pip
+
+```bash
+pip install earth2studio[cosmo]
+```
+
+:::
+:::{tab-item} uv
+
+```bash
+uv add earth2studio --extra cosmo
+```
+
 :::
 ::::
 :::::

earth2studio/models/dx/__init__.py

@@ -24,6 +24,7 @@
     CorrDiffTaiwan,
 )
 from earth2studio.models.dx.corrdiff_cmip6 import CorrDiffCMIP6
+from earth2studio.models.dx.cosmo_downscaling import CosmoDownscaling  # noqa
 from earth2studio.models.dx.derived import (
     DerivedRH,
     DerivedRHDewpoint,
@@ -54,6 +55,7 @@
     "CorrDiff",
     "CorrDiffCMIP6",
     "CorrDiffTaiwan",
+    "CosmoDownscaling",
     "DLESyMv0_ISCCP_ERA5Precip",
     "PrecipitationAFNO",
     "PrecipitationAFNOv2",