ERA5 (``ERA5``)
===============

**Upstream:** **Copernicus Climate Data Store (CDS)** via `cdsapi <https://cds.climate.copernicus.eu/>`_. Retrieval uses the CDS API (not presigned HTTP URLs from :func:`coldcast.download.download_requests`).

**Transport:** :func:`coldcast.sources.era5.download` calls ``cdsapi.Client().retrieve()`` into ``output_dir``.

**Auth:** ``~/.cdsapirc`` with CDS URL and API key.

**CLI:** ``coldcast download era5 [--run-info-netcdf …]``

**Settings:** Under the unified ``ECMWF`` block, product key ``ERA5`` — ``num_days_back``, ``delay_days``, ``variables_surface_level``, ``grid``, ``hours``. A legacy top-level ``ERA5`` block is still read if present. Geographic extent: merge of top-level ``bounding_box`` and the product’s ``bounding_box`` or ``bbox`` (CDS sequence or ``lon_min`` / ``lon_max`` / ``lat_min`` / ``lat_max``); nested keys override the global defaults per coordinate.

**Code:** :mod:`coldcast.sources.era5`