Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

Abstract

Abstract. At Uccle, Belgium, a long time series of simultaneous measurements of erythemal ultraviolet (UV) dose (S ery ), global solar radiation (S g ), total ozone column (Q O 3 ) and aerosol optical depth (τ aer ) (at 320.1 nm) is available, which allows for an extensive study of the changes in the variables over time. Linear trends were determined for the different monthly anomalies time series. S ery , S g and Q O 3 all increase by respectively 7, 4 and 3 % per decade. τ aer shows an insignificant negative trend of −8 % per decade. These trends agree with results found in the literature for sites with comparable latitudes. A change-point analysis, which determines whether there is a significant change in the mean of the time series, is applied to the monthly anomalies time series of the variables. Only for S ery and Q O 3 , was a significant change point present in the time series around February 1998 and March 1998, respectively. The change point in Q O 3 corresponds with results found in the literature, where the change in ozone levels around 1997 is attributed to the recovery of ozone. A multiple linear regression (MLR) analysis is applied to the data in order to study the influence of S g , Q O 3 and τ aer on S ery . Together these parameters are able to explain 94 % of the variation in S ery . Most of the variation (56 %) in S ery is explained by S g . The regression model performs well, with a slight tendency to underestimate the measured S ery values and with a mean absolute bias error (MABE) of 18 %. However, in winter, negative S ery are modeled. Applying the MLR to the individual seasons solves this issue. The seasonal models have an adjusted R 2 value higher than 0.8 and the correlation between modeled and measured S ery values is higher than 0.9 for each season. The summer model gives the best performance, with an absolute mean error of only 6 %. However, the seasonal regression models do not always represent reality, where an increase in S ery is accompanied with an increase in Q O 3 and a decrease in τ aer . In all seasonal models, S g is the factor that contributes the most to the variation in S ery , so there is no doubt about the necessity to include this factor in the regression models. The individual contribution of τ aer to S ery is very low, and for this reason it seems unnecessary to include τ aer in the MLR analysis. Including Q O 3 , however, is justified to increase the adjusted R 2 and to decrease the MABE of the model.

Reconstruction and analysis of erythemal UV radiation time series from Hradec Králové (Czech Republic) over the past 50 years

“…3d) was only affecting the EUV radiation doses in winter months; therefore, its effect throughout the decades was the weakest of all the studied variables (r part ranging from 0.16 in the decade 1984-1993 to 0.25 in the decade 2004-2013). The results concur with similar studies performed at other European locations, showing that TOC is the main driver of long-term EUV radiation changes, while SZA and cloud cover are the dominant factors affecting EUV radiation in the short term (Den Outer et al, 2010;Herman, 2010;De Bock et al, 2014). The changes in EUV radiation in the 1970s have been attributed to cloud cover variability, which is in accord with the high r part shown in Fig.…”

“…According to numerous studies, atmospheric circulation and stratospheric temperature greatly affect the intensity of global ozone losses (e.g., Orsolini and Limpasuvan, 2001;Schnadt and Dameris, 2003;Hofmann et al, 2009). In the 1970s-1990s, TOC trends in central Europe showed a decline by about 3-4 % per decade, especially in spring, while the recovery of the ozone layer has been reported since the end of the 1990s (e.g., Krzyścin et al, 1998;Krzyscin and Borkowski, 2008;Vaníček et al, 2012;De Bock et al, 2014).…”

Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

“…Signs from the onset of ozone recovery since the late 1990s on surface UV-B irradiance have been mainly detected over the northern high latitudes; recent studies indicate that UV-B has been declining during the last 2 decades (Bernhard, 2011;Eleftheratos et al, 2014). However, during the same period, both the UV-B and the UV-A irradiance are increasing over many locations in the Northern Hemisphere mid-latitudes, mainly due to the negative trends in the amount of clouds and aerosols (De Bock et al, 2014;Fitzka et al, 2012;Román et al, 2015;Smedley et al, 2012;Zerefos et al, 2012). In a recent study, Fragkos et al (2015) showed that in Thessaloniki, even under extreme high (low) total ozone column (TOC) conditions, the erythemal irradiance can be lower (higher) than its climatological values due to the dominant effect of aerosols.…”

Effects of urban agglomeration on surface-UV doses: a comparison of Brewer measurements in Warsaw and Belsk, Poland, for the period 2013–2015

“…Upward UVB and UVA trends have been reported over several mid-latitudinal sites of the Northern Hemisphere since the beginning of the 1990s, which have been mainly attributed to decreasing attenuation by aerosols and clouds (e.g. Krzyścin et al, 2011;Zerefos et al, 2012;De Bock et al, 2014).…”