Evaluation of Erythemal ultraviolet solar radiation over Saudi Arabia Zaki A. Al-Mostafa a,b,⇑ , Hamdy K. Elminir c , Ahmed Abulwfa d , Saad M. Al-Shehri a,b , Fawaz A. Alshehri a , Ibrahim M. Al-Rougy e , Ahmed A. Bazyad a a King Abdulaziz City for Science and Technology, National Astronomy Center, P.O. Box 6086, Riyadh 11442, Saudi Arabia b King Abdullah Bin Abdulaziz Chair for Crescent Observations and Lunar Research “KACCOLR”, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia c Kafr Elshiekh University, Department of Electrical Engineering, Faculty of Engineering, 33735 Kafr Elshiekh, Egypt d National Research Institute of Astronomy and Geophysics, Department of Solar Research, 11421 Helwan, Egypt e King Abdulaziz City for Science and Technology, Oil and Gas Center, P.O. Box 6086, Riyadh 11442, Saudi Arabia Received 2 September 2014; received in revised form 14 December 2014; accepted 8 January 2015 Communicated by: Associate Editor Jan Kleissl Abstract To characterize and reduce the harmful effects of Erythemal ultraviolet radiation (EUV), it is vital to recognize the spatial distribution and temporal variation of EUV radiation under various meteorological conditions. In light of these requirements, the problem we address here is to understand the results of a study performed to assess the influence of stratospheric ozone and aerosol loading on the receipt of EUV at six sites located in Saudi Arabia. The selected sites were chosen to represent the climatic zones of the north, middle, and south of Saudi Arabia. Intensive satellite-based measurements of the atmosphere over the period 1979–2005 obtained from the Total Ozone Mapping Spectrometer (TOMS) website (ftp://toms.gsfc.nasa.gov) were used, with a four year gap from 1993 to 1996. The results hint that, in spite of the significant decrease in stratospheric ozone, there is a clear decreasing trend in the EUV data series due to the increase in the aerosol loading during summer months. For the other months the correlation is not clear and in all cases there was no decrease in the EUV radiation trend outside summer months, with few exceptions. Ó 2015 Elsevier Ltd. All rights reserved. Keywords: Erythemal ultraviolet radiation (EUV); Total Ozone Mapping Spectrometer (TOMS); Stratospheric ozone; Total Ozone Column (TOC); Aerosol index (AI); Saudi Arabia 1. Introduction and objectives Based on the definition of (GES DISC) – Goddard Earth Sciences Data and Information Services Center – Erythemal UV Exposure is a measure of the potential for biological damage due to solar ultraviolet radiation. TOMS’ Erythemal exposure is calculated using UV irradi- ance reaching the surface of earth (deduced from measured UV irradiance entering the atmosphere, TOMS’ total Ozone Column and Surface Reflectivity) and weighted by the model value of the susceptibility of Caucasian skin to sunburn (erythema). In spite of the importance of the sun in reducing the syndromes of some cases of skin diseases, such as psoriasis and vitiligo, it is prudent to limit exposure to solar ultraviolet (UV) radiation. The cumulative effects of exposure to UV radiation are largely responsible for the destruction of collagen protein fibers, which accelerates aging of the skin. Other UV-related skin disorders include http://dx.doi.org/10.1016/j.solener.2015.01.010 0038-092X/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: King Abdulaziz City for Science and Technology, National Astronomy Center, P.O. Box 6086, Riyadh 11442, Saudi Arabia. Tel.: +966 114813575; fax: +966 114813521. E-mail address: zalmostafa@kacst.edu.sa (Z.A. Al-Mostafa). www.elsevier.com/locate/solener Available online at www.sciencedirect.com ScienceDirect Solar Energy 113 (2015) 258–271