Global (G) and diffuse (G(d)) shortwave and global erythemal (UVER) horizontal irradiances and atmospheric components like, total ozone column, water vapour column, aerosol optical depth were measured in Malta, at the Institute for Sustainable Energy in the south-eastern village of Marsaxlokk, in the middle of Mediterranean Sea. The effect of solar zenith angle on these irradiances is studied using the measurements and simulations developed with a radiative transfer model. Horizontal global and beam (G(b)) irradiances show a linear relation with zenith solar angle cosine. The role of ozone, scattering by gases, and aerosols is analysed. Simulation model results show that total ozone column, aerosol optical depth and Rayleigh scattering are the main drivers responsible for the behaviour of UVER variations with solar zenith angle (SZA). In the case of global and diffuse shortwave irradiance, the effect of aerosols is the principal determinant. (C) 2015 Elsevier Ltd. All rights reserved.