Abstract
Abstract. The daily doses of the erythemally weighted UV radiation are reconstructed for three sites in Central Europe: Belsk-Poland (1966–2001), Hradec Kralove-Czech Republic (1964–2001), and Tõravere-Estonia (1967–2001) to discuss the UV climatology and the long-term changes of the UV-B radiation since the mid 1960s. Various reconstruction models are examined: a purely statistical model based on the Multivariate Adaptive Regression Splines (MARS) methodology, and a hybrid model combining radiative transfer model calculations with empirical estimates of the cloud effects on the UV radiation. Modeled long-term variations of the surface UV doses appear to be in a reasonable agreement with the observed ones. A simple quality control procedure is proposed to check the homogeneity of the biometer and pyranometer data. The models are verified using the results of UV observations carried out at Belsk since 1976. MARS provides the best estimates of the UV doses, giving a mean difference between the modeled and observed monthly means equal to 0.6±2.5%. The basic findings are: similar climatological forcing by clouds for all considered stations (~30% reduction in the surface UV), long-term variations in UV monthly doses having the same temporal pattern for all stations with extreme low monthly values (~5% below overall mean level) at the end of the 1970s and extreme high monthly values (~5% above overall mean level) in the mid 1990s, regional peculiarities in the cloud long-term forcing sometimes leading to extended periods with elevated UV doses, recent stabilization of the ozone induced UV long-term changes being a response to a trendless tendency of total ozone since the mid 1990s. In the case of the slowdown of the total ozone trend over Northern Hemisphere mid-latitudes it seems that clouds will appear as the most important modulator of the UV radiation both in long- and short-time scales over next decades. Key words. Atmospheric composition and structure (biospheric-atmosphere interaction) – Meteorology and atmospheric dynamics (climatology; radiative processes)
Highlights
The ultraviolet (UV) radiation reaching the ground is only a small portion of the radiation received from the Sun but extremely important for the Earth’s ecosystem
We examine two categories of the reconstruction models, i.e. a purely statistical model based on the Multivariate Adaptive Regression Splines (MARS) methodology and a model combining radiative transfer calculations for clear-sky conditions with the empirically derived cloud reduction factor of the UV radiation derived from the attenuation of total solar radiation
The reconstruction models examined here are capable of reproducing low-frequency variations of the monthly mean surface UV doses
Summary
The ultraviolet (UV) radiation reaching the ground is only a small portion of the radiation received from the Sun but extremely important for the Earth’s ecosystem. Kerr and McElroy, 1993, Borderwijk et al, 1995; Zerefos et al, 1995; Krzyscin, 1996; Weatherhead et al, 1997; Udelhofen et al, 1999; den Outer et al, 2000; Kaurola et al, 2000; Matthijsen et al, 2000; Eerme et al, 2002) These studies confirm that the UV changes are driven by various factors: ozone, cloudiness, aerosols, and surface albedo. The reconstructed data sets, which can extend backward in time to the beginning of total ozone and pyranometer or cloud observations, would help to examine the climatology and the long-term variations and trends of UV radiation (Kaurola et al, 2000; Fioletov et al, 2001).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
