Evolution of erythemal and total shortwave solar radiation in Valladolid, Spain: Effects of atmospheric factors

Erythemal ultraviolet (UVER; 280–400 nm) and total shortwave (SW; 305–2800 nm) solar irradiances were recorded from 2000 to 2009 in Valladolid, Spain. UVER and SW values under cloudless conditions are simulated by radiative transfer (TUV 4.6) and empirical models. These model estimations are tested with experimental measurements showing a great agreement (root mean square error around 7%). The aerosol effect on UVER irradiance is determined through a model study. UVER radiation and total ozone column (TOC) temporal evolutions show a negative relationship. TOC accounts for 80% of UVER variance and its radiation amplification factor is 1.1 at zenith of 65°. Cloud effects on solar radiation are shown and quantified by the cloud modification factor. Moreover the enhancement effect cases are analysed. SW radiation proves more sensitive to clouds than UVER. Clouds are seen to attenuate and enhance solar radiation by up to 93% and 22% in the UVER range, respectively.

Research Highlights
► The time evolution of erythemal radiation in Valladolid (Spain) is analyzed.
► A radiative transfer model is validated.
► Clouds, aerosols and ozone can change erythemal levels on surface.
► Ozone effect on erythemal is quantified using the RAF.
► Cloud enhancement effect is quantified in total shortwave radiation.