Update CAMS references & motivate why PVLIB uses CAMS radiation time series access

[mschroedter]

Dear pvlib team,

A) CAMS re-arranged its web page. Therefore, reference [1] on
https://pvlib-python.readthedocs.io/en/stable/reference/generated/pvlib.iotools.get_cams.html#id9
as well as on
https://pvlib-python.readthedocs.io/en/stable/reference/generated/pvlib.iotools.read_cams.html#pvlib.iotools.read_cams
and on
https://pvlib-python.readthedocs.io/en/stable/reference/generated/pvlib.iotools.get_cams.html#id9
links currently to an outdated CAMS web page. I can see that issue #1515 recommended indeed this web link, but recent re-arrangement on the CAMS webpage made this now an outdated link.

All references [1] better would link to https://ads.atmosphere.copernicus.eu/datasets/cams-solar-radiation-timeseries.
From there description, extended documentation and validation data can easily be found.

B) Recently CAMS made a gridded solar radiation dataset (https://ads.atmosphere.copernicus.eu/datasets/cams-gridded-solar-radiation) available, which consists of many CAMS time series pre-calculated and made available in monthly files. Please note, that this CAMS gridded radiation dataset will only be updated/extended by the last data year once a year with approx. 6 months delay, while the CAMS time series access has updated data with a day delay only. Therefore, it is recommended for PVlib users interested in single locations to use CAMS time series as done before.

To avoid confusion I suggest to rename reference [1] on all 3 pages named in section [A] of this issue to 'CAMS solar radiation time series documentation'.

C) Furthermore, I would like to suggest additional text in the documentation to clarify the difference of CAMS time series and gridded data. New text could be:

“Time-series of radiation and/or clear-sky global, beam, and diffuse radiation from CAMS (see [1]). Data is retrieved from SoDa [2]. Please note, that CAMS gridded dataset (see [4]) is a post-processed compilation of many pre-calculated CAMS time series on a pre-defined 10 km/15 min grid over land and coastal areas, and may therefore not yet include the most recent software and data coverage. Therefore, the CAMS time series access is continued to be used in PVLIB.”

This would be the added reference
[4] CAMS gridded solar radiation documentation
linking to https://ads.atmosphere.copernicus.eu/datasets/cams-gridded-solar-radiation

Thank you for your support in advance.

[kandersolar]

Thank you @mschroedter for bringing this up! I've tagged this for our next release so that we remember to make these changes. You are very welcome to submit a PR yourself if you want, otherwise I think @AdamRJensen is the best person to make these updates.

[AdamRJensen]

I'll take care of this!