Spectral UV measurements in Austria from 1994 to 2006: investigations of short- and long-term changes S. Simic, P. Weihs, A. Vacek, H. Kromp-Kolb, and M. Fitzka Institute of Meteorology, University of Natural Resources and Applied Life Sciences (BOKU), Vienna, Austria
Abstract. The influence of variability of atmospheric parameters on short- and
long-term changes of spectral UV irradiance measured at the Sonnblick
observatory (47.03° N, 12.57° E, 3106 m) during the period from 1994 to 2006
is studied. Measurements were performed with the Brewer #093
single-monochromator spectrophotometer and with a Bentham DM 150
The influence of ozone, albedo, snowline and clouds on UV variability is
evaluated for each parameter separately using 10-year climatology. It is
found that the effect of total ozone on short-term variability of UV
irradiance at 305 nm can be more than 200% and on average more than
50%. Clouds can cause variability of 150% or more and on average
35%. Variability caused by albedo reaches a maximum of 32% in April
(6% on average). In summer and autumn, total ozone and clouds strongly
influence the variability of UV radiation, whereas in winter and spring
ozone has the more pronounced effect. A decrease in snowline height from
3000 m to 800 m a.s.l. enhances the UV irradiance by a factor of 1.24 for
clear sky conditions and by a factor of 1.7 for 8/8 cloud cover.
Long-term trends are investigated for the time period from 1994 to 2006
based on clear-sky measurements, using the non-parametric Mann-Kendall trend
test. Significant downward trends (99% confidence level) are found for
solar zenith angle 55° at wavelengths from 305 nm to 324 nm and
erythemally weighted irradiance according to CIE, which are caused by an
increase in sunshine duration during periods of high total column ozone.
Significant trends (90% confidence level) were also found for other
combinations of wavelength and SZA.
Citation: Simic, S., Weihs, P., Vacek, A., Kromp-Kolb, H., and Fitzka, M.: Spectral UV measurements in Austria from 1994 to 2006: investigations of short- and long-term changes, Atmos. Chem. Phys., 8, 7033-7043, doi:10.5194/acp-8-7033-2008, 2008.