Ratio of UV to global broad band irradiation in Valencia, Spain

This paper presents the results of an analysis of 6 years of measurements of UV and broad band irradiation values in Valencia, Spain. Hourly and daily integrated UV irradiance, ITUV, measured by a TUVR Eppley radiometer, and global irradiance IT from a Kipp-Zonen CM-11 pyranometer, were highly correlated, with ITUV/IT percentages varying from 2.9% to 3.5% for hourly values and from 2.9% to 3.4% for daily values. If a general linear relation ITUV=mIT is considered, the correlation coefficient r is always greater than 0.96 for hourly values and 0.91 for daily values. However, the relation between ITUV/IT and the clearness index kT is poorly correlated, although improved results, with less dependence on a specific location, can be observed using the kTUV and kT clearness indices. For a general linear relation, kTUV=mkT, the correlation coefficient r is always greater than 0.89 for hourly values and 0.86 for daily values.