Solar UVR instrument inter-comparison focussing on measurement interval recording setting and solar zenith angle as important factors

Abstract

Solar ultraviolet radiation (UVR) data for matching time periods between November 2014 and February 2015 were recorded by two instruments, namely a UVR biometer and a Davis UVR sensor, and their data were compared. Several checks and challenges were identified during the data preparation stage. The measurement interval of the biometer was changed from 30-minutes to 1 hour which prompted the recalculation of readings measured by the Davis UVR sensor for the periods affected. On average, the Davis UVR sensor slightly overestimated solar UVR levels when compared to the biometer data and this relationship was strongest for small solar zenith angles when the sun was high in the sky. Further research is necessary to investigate the influence of other external factors that may influence the differences in the two instruments solar UVR measurements, such as instrument hardware in the form of fins on the Davis UVR sensor housing.