Quality control procedure for 1-minute pyranometric measurements of global and shadowband-based diffuse solar irradiance

A novel automatic filtering methodology is proposed for 1-min GHI and DIF data using surface measurements obtained at five sites located in various climate zones of Argentina. The methodology contemplates DIF information obtained through the use of a shadowband or shading ring instead of the shading ball that requires a solar tracker. Three different flags are presented for suspicious or erroneous data identified by the filters of the methodology, which respond to the weight or strictness of the corresponding filter. The methodology uses filters established in the literature and proposes new filters capable of identifying slight misalignments of the shadowband as well as measurements below a minimum threshold empirically established for heavily overcast or thunderstorm conditions. A statistical analysis based on data obtained at a high-quality reference station and the modification of a pre-existing methodology is also presented. In general terms and at all sites, it is observed that the total amount of suspicious data increases significantly as the solar zenith angle increases. Overall, the methodology is able to identify and flag 15.0–44.6% erroneous or suspicious values, depending on site. The proposed methodology is applicable at any world station where the global and diffuse irradiance components are both measured.