This activity focuses on collection of high quality ground measurements which can be used as a reference in the benchmarking exercises. The measurements should be conducted with high accuracy, high frequency and traceable maintenance of the equipment. Data has been collected from the Baseline surface radiation network (BSRN), International Daylight Measurement programme (IDMP), the meteomedia network, the World Radiation Data Center (WRDC) and the Global Atmospheric Watch (GAW) programme. In addition further measurements were collected from scientific institutions, providing they fulfil the quality criteria above.

A common quality control procedure has been defined for all broadband time series data. The parameters for the quality assessment have been deducted from the Baseline Surface Radiation Network Operation Manual [3] and operational experience of the partners involved. All data is flagged if:

• It is within the physical possible limits. The applied physical limits are shown in table 1.

• It is lower than it would be in a dry and clean atmosphere. We apply the e. g. the Bird clear sky model (Model C in [4]) with aerosols and water vapour set to zero.

• The components of direct, diffuse and global parameters are coherent (if all are available). The conditions and limits are described in table 2.

Only values passing all tests will be used in the benchmarking exercises.