ИСТИНА

Abstract: Continuous measurements of biological active erythemal UV radiation have been started at Meteorological Observatory of Moscow State University by broadband radiometers since 1999. To maintain high quality of measurements, checking of calibration coefficients is regularly carried out. Twice a year, a comparison with control devices, which, in turn, are calibrated against European standards, takes place. It was revealed that one of the used UVB-1 YES devices had noticeable temperature dependence in conditions of cold period of year (20-30% underestimation of measurements). Therefore, special correction of its measurements, based on air temperature and model calculations, was developed. In addition, rigorous research of calibration coefficient for another device that had been used in the beginning of measurements was carried out and additional correction of its measurements (+/-2%) for 2000 and 2003 years was accomplished by the use of model calculations. Variability of erythemal UV radiation and factors influencing it were analyzed based on the corrected measurements. Maximum values of UV index reach 6-7 in Moscow. We showed that the average annual erythemal UV radiation attenuation due to cloudiness and total ozone content are approximately equal in Moscow conditions. The maximal loss of erythemal UV radiation due to cloudiness is observed in November, while ozone-dependent attenuation is maximal in February– March. We also analyzed statistical parameters of UV radiation variability. The kurtosis of daily erythemal UV doses is statistically significant positive from November to February and negative from March to September. The skewness of daily erythemal UV doses is characterized by significantly positive values from September to April and negative values from May to August due to changes in cloud conditions throughout the year. Relative variability of yearly UV radiation doses in comparison with average value is low in recent years. Acknoledgments: The work was partially supported by RFBR, research project No. 18-05-00700 a.