At ETH Zurich, a central flagging of the data quality was performed. The flags and the derived global radiation (calculated from direct and diffuse) were included in the station-to-archive files. It was up to the user to follow or to disregard these static flags. During the transition of the WRMC from ETH Zurich to the AWI (end of 2007) the central flagging of the data quality was terminated. All station-to-archive files in the WRMC have nowadays exactly their native format as given from their station scientists who are responsible for the quality of the submitted data. The quality checks which are now offered at AWI are implemented as flexible post prozess which can be adapted to the individual demands of a variety of users with different aims.

The quality of many BSRN data can be controlled individually by using the newest version of the BSRN Toolbox which was first released in 2012. The tool is rather flexible. It can handle:

• station-to-archive files freshly created by a station scientists prior to submission,
• files downloaded from the ftp-archive (ftp://ftp.bsrn.awi.de/),
• files downloaded from PANGAEA,
• files created via the DataWarehouse (for longer timeseries).

The quality checks offered by the BSRN Toolbox can help:

• the station scientists to test station-to-archive files before they get submitted,
• the data curator from the WRMC to perform quality checks before archiving the data (this gets done routinely since December 2011), and
• any user of the WRMC to test extracted data from the WRMC.

The quality checks are implemented into the BSRN Toolbox by Holger Schmithüsen. At the moment the BSRN Toolbox offeres the BSRN Global Network recommended QC tests, V2.0 from C. N. Long and E. G. Dutton. In the future, more qualitiy check options will be developed and implemented.

More detailed information are given at: http://wiki.pangaea.de/wiki/BSRN_Toolbox#Quality_Check.

There are of course many other initiatives for quality checks of solar data, a few of them are listed here (you are free to propose additions, just write us an E-Mail):

https://pypi.org/project/pybsrnqc/
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https://assessingsolar.org/notebooks/quality_asessment.html
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https://github.com/YvesMSaintDrenan/IEA_PVPS_T16_QC_pynb/blob/master/03_SolarDataQC.ipynb
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https://github.com/dazhiyang/SolarData (see Yang D. 2018. SolarData: An R package for easy access of publicly available solar datasets, Solar Energy 171, doi:10.1016/j.solener.2018.06.107 and Yang, D. 2019. SolarData package update v1.1: R functions for easy access of Baseline Surface Radiation Network (BSRN), Solar Energy, 188, doi:10.1016/j.solener.2019.05.068)
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http://www.bqcmethod.com/ (Urraca R, Sanz-Garcia I, Sanz-Garcia A. 2020. BQC: a free web service to quality control solar irradiance measurements over Europe. Solar Energy, 211, doi:10.1016/j.solener.2020.09.055)
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