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Data Access

Several TARSA examples and validation cases download external data. This page collects the required credentials in one place so the rest of the documentation can stay short.

ERA5 through Copernicus CDS

ERA5 downloads used by TARSA.prepare_input_data(...) require Copernicus CDS credentials. Use one of these two patterns:

Option 1: ~/.cdsapirc

Create ~/.cdsapirc with:

url: https://cds.climate.copernicus.eu/api
key: <your-uid>:<your-api-key>

This is the simplest setup for local use and the default path used in the TARSA guides.

Option 2: environment variables

You can also export the credentials directly:

export CDSAPI_URL=https://cds.climate.copernicus.eu/api
export CDSAPI_KEY=<your-uid>:<your-api-key>

This is useful for clusters, CI, or temporary shells.

CAMS through Copernicus ADS

CAMS downloads require ADS credentials when rebuilding external data products outside the current prepare_input_data helper. Built-in CAMS regridding is currently disabled, so TARSA workflows that need CAMS fields expect a pre-regridded NetCDF file. The same two credential patterns work for any external rebuild scripts:

Option 1: ~/.cdsapirc

url: https://ads.atmosphere.copernicus.eu/api
key: <your-uid>:<your-api-key>

Option 2: environment variables

export CDSAPI_URL=https://ads.atmosphere.copernicus.eu/api
export CDSAPI_KEY=<your-uid>:<your-api-key>

The TARSA download helpers switch the required API URL internally when moving between ERA5 and CAMS.

NASA Earthdata / GES DISC

The FENNEC example runs from a prepared input bundle and does not need NASA credentials for normal use. Earthdata credentials are only needed if you rebuild the MERRA-2 inputs that feed that bundle.

Use either ~/.netrc or environment variables expected by the rebuild scripts:

export EARTHDATA_USER=<username>
export EARTHDATA_PASS=<password>

Make sure the GES DISC application is authorized for the account before requesting MERRA-2 products.

First-run guidance

  • The shipped tutorial meteorology under examples/tutorial/data/ means the tutorial usually runs without any credentials at all.
  • You only need Copernicus access if you delete those cached files or run a case that downloads ERA5 itself.
  • CAMS and MERRA-2 products are normally consumed from prepared or externally regridded files in the current examples.
  • If a TARSA download step fails immediately, first check that the URL matches the dataset family you are requesting: CDS for ERA5, ADS for CAMS.