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

Abstract

A statistical analysis and inter-comparison of the broadband ultraviolet-A (UVA) 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 UVA irradiation and their frequency distribution at both sites are computed and discussed. Daily maximum of hourly average irradiance values occur in July, 58W m-2 and minimum, 22 W m-2, in December at solar noon at Athalassa. The respective values at Larnaca are slightly higher (68 W m-2 and 28 W m-2, respectively). UVA daily values follow the pattern of the solar altitude angle; the total accumulated UVA irradiation along a mean year reaches 385.8 MJ m-2 at Athalassa and 476.5 MJ m-2; maximum stability of UVA takes place at midday hours and during the summer. Large fluctuations of the daily UVA irradiation are observed in the winter and spring months, which are mainly due to unstable meteorological conditions during the transition from cold to warm weather and vice versa. During summer the daily UVA radiation exceeds the value of 1700 kJ m-2 at Athalassa and 2100 kJ m-2 at Larnaca, while during the winter season the lowest is about 250 kJ m-2 at both stations. The UVA potential and extraterrestrial irradiation have also been calculated in order to estimate the attenuation of UVA radiation through the atmosphere. The UVA transmittance, kUVA, is approximately 6 to 7% of the hemispherical transmittance for the whole spectrum (kt). Statistical relationships between UVA and other radiation components were established using linear or power relationships.