Statistical Analysis and Inter-Comparison of Solar UVB and Global Radiation for Athalassa and Larnaca, Cyprus

Abstract

A statistical analysis and inter-comparison of the broadband ultraviolet-B (UVB) radiation at two sites in Cyprus representing two different climate regimes of the island (Athalassa-inland plain vs Larnaca-coastal location) covering the period January 2013-December 2015 is presented. Mean annual and mean monthly daily totals of the UVB irradiation and their frequency distribution at both sites are computed and discussed. Daily maximum of hourly average irradiance values occur in July, 2.09 W m-2, and minimum, 0.47 W m-2, in December at solar noon at Athalassa. The respective values at Larnaca are slightly higher (2.48 W m-2 and 0.67 W m-2, respectively). UVB daily values follow the pattern of the solar altitude angle; the total accumulated UVB irradiation along a mean year reaches 10.27 MJ m-2 at Athalassa and 13.49 MJ m-2; maximum stability of UVB takes place at midday hours during the summer. Large fluctuations of the daily UVB irradiation are observed in the spring months and November, which are mainly due to unstable meteorological conditions during the transition from cold to warm weather and vice versa. During summer the daily UVB radiation exceeds the value of 70 kJ m-2 at Larnaca and 55 kJ m-2 at Athalassa, while during the winter season the lowest is about 5 kJ m-2 at both stations. The UVB potential and extraterrestrial irradiation has also been calculated in order to estimate the attenuation of UVB radiation through the atmosphere. During summer the UVB transmittance is higher than in winter with a maximum value of 9% in July and a minimum of about 4% in December. Statistical relationships between UVB and other radiation components (UVA and global radiation) were established.