Ground Based Measurements of Solar UV Index in Tabriz

Introduction: Ultraviolet index (UVI) is a dimensionless scale, which describes the maximum intensity and biologic effects of UV during a specific time, on surface of the earth. The UVI is  an  international  standard measurement of  the  strength  of sunburn  producing ultraviolet radiation at a particular place and time. This index is an easy and understandable concept for protection and application for people, which can be described: 2 or less means low exposure, 3-5 means average, 6-7 means high, 8-10 means very high and more than that means dangerous. The major approach is to calculate UVI by measuring the intensity of UV exposure on the surface of earth. In this study we calculated the UVI at Tabriz, based on the measurement of UV intensity. Materials and Methods: First, the amounts of UV type A and B by handheld lux UV-IR meter, for a whole year from sunrise to sunset were measured in Tabriz during 2016-2017. We use the following formula to calculate UVI: UVI  k er  ò  E l .w(l)d (l)                                                                  (1-1) 400   250     ìw(l ) = 1.........................250 < l < 298 ï             0.094 ( 298 - l ) íw(l ) = 10           ..........298 < l < 328                                               (1-2) ïw(l ) = 100.015 (139 - l )..........328 < l < 400 î In which Eλ is the intensity of the specific wavelength reaching the earth, ω(λ) is the biological effect of the specific wavelength and Ker is a constant which is 40 m2/W. Results: Our results showed that the maximum UVI occurs between 12 and 13 o'clock. Maximum and minimum Data was obtained in May and January respectively. For the summer and spring months, the amount of UVI is more than 10 in the 12 to 15 hours. In Just two month of the year, UVI is less that average, even in noon. Conclusion: Except for winter, UV exposure is high in noon (12 to 15 o'clock) and we recommend avoiding the direct sun exposures.