Add SYNDA drs for CMIP5 and CMIP6 (closes #582)

[zklaus]

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Closes #582

[bouweandela]

Note that the paths that synda creates appear to be configurable: http://prodiguer.github.io/synda/sdt/selection_file_param_ref.html#synda-formatting-parameters
I guess this would be the default directory structure?

Maybe it would also be nice to add a note about this in the documentation somewhere? We have two relevant sections, https://esmvaltool.readthedocs.io/en/latest/input.html and https://esmvaltool.readthedocs.io/projects/esmvalcore/en/latest/quickstart/find_data.html.

[zklaus]

Yes, this is the default structure. Note also that the configuration that you link to above is per selection file. This is not the only, perhaps not even the most common way to download using the daemon.

I'll see about the documentation.

[valeriupredoi]

@bouweandela yes - K-man is right since we are using synda get in our module which is the basic no-checks command that gets the files noqa 🍺

[stefsmeets]

Hi @ESMValGroup/esmvaltool-coreteam , seems like this PR has been sitting around approved and ready to go for a while 😅 It's a two line fix, can this just be merged?

[bouweandela]

No, the documentation has still not been added.

[stefsmeets]

No, the documentation has still not been added.

Thanks @bouweandela , I added a short paragraph to the esmvalcore documentation 👍
https://esmvaltool--583.org.readthedocs.build/projects/ESMValCore/en/583/quickstart/find_data.html#synda

[bouweandela]

Thanks @stefsmeets for wrapping this up!