We studied the trends of UV index in the city of Novi Sad (latitude 45.3N, longitude 19.8 E at the 80m height) in the 2004-2013 time period. The measurements of UV index were performed with the Yankee Environmental System (YES) UVB-1 pyranometer. The linear regression method was used to calculate the trends of UV index. The yearly trend of UV index from the relative monthly differences considered with climatological value was investigated. We obtained the positive yearly UV trend of 7.9±1.7% per decade at the location of Novi Sad. Further on, the monthly UV trends were investigated. We obtained significant positive trends in April, August, October and December, with no significant negative UV trends.

1. A. F. McKinlayandB. L. Diffey, "A reference action spectrum for ultraviolet induced erythema in human skin," CIE J. vol. 6, pp. 17–22, 1987.
2. A. Arola, K. Lakkala, A. Bais, J. Kaurola, C. Meleti, and P. Taalas, "Factors affecting short- and long-term changes of spectral UV irradiance at two European stations," J. Geophys. Research Atmosph., vol. 108, no. D17, p. 4549, Sep. 2003.
   DOI: 10.1029/2003JD003447
3. R. M. Lucas, M. Norval, R. E. Neale, A. R. Young, F. R. de Gruijl, Y. Takizawa, and J. C. van der Leun, "The consequences for human health of stratospheric ozone depletion in association with other environmental factors," Photochem. Photobiol. Sci., vol. 14, no. 1, pp. 53-87, 2015.
   DOI: 10.1039/C4PP90033B
   PMid: 25383760
4. B K. Dichter, A. F. Beaubien and D. J. Beaubien, "Development and Characterization of a New Solar Ultraviolet-B Irradiance Detector," J. Atmos. Oceanic Technol., vol. 10, pp. 337–344, 1993.
   DOI: 10.1175/1520-0426(1993)010<0337:DACOAN>2.0.CO;2
5. S. Simic, Weihs, P., Vacek, A., Kromp-Kolb, H., and M. Fitzka, "Spectral UV measurements in Austria from 1994 to 2006: investigations of short- and long-term changes," Atmos. Chem. Phys., vol. 8, pp. 7033-7043, Dec. 2008.
   DOI: 10.5194/acp-8-7033-2008
6. M. R. Schoeberl et al., “Overwiev of the EOS Aura Mission,” IEEE Trans. Geosci. Remote. Sens., vol. 44, no. 5, pp. 1066-1074, 2006.
   DOI: 10.1109/TGRS.2005.861950
7. M. Fitzka, S. Simic, and J. Hadzimustafic, "Trends in spectral UV radiation from long-term measurements at Hoher Sonnblick, Austria," Theor. Appl. Climatol., vol. 110, no. 4, pp. 585-593, 2012.
   DOI: 10.1007/s00704-012-0684-0
8. V. De Bock, H. De Backer, R. Van Malderen, A. Mangold, and A. Delcloo, "Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium," Atmos. Chem. Phys., vol. 14, no. 22, pp. 12251-12270, 2014.
   DOI: 10.5194/acp-14-12251-2014
9. I. Fountoulakis, A. F. Bais, K. Fragkos, C. Meleti, K. Tourpali, and M. M. Zempila, "Shortand long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: Effects of changes in aerosols, total ozone and clouds," Atmos. Chem. Phys. Discuss., vol. 15, no. 24, pp. 35753-35785, 2015.
   DOI: 10.5194/acpd-15-35753-2015