Global dimming and brightening versus atmospheric column transparency, Europe, 1906–2007

Abstract

Multiannual changes in atmospheric column transparency based on measurements of direct solar radiation allow us to assess various tendencies in climatic changes. Variability of the atmospheric integral (broadband) transparency coefficient, calculated according to the Bouguer‐Lambert law and transformed to a solar elevation of 30°, is used for two Russian locations, Pavlovsk and Moscow, one Ukrainian location, Feodosiya, and three Estonian locations, Tartu, Tõravere, and Tiirikoja, covering together a 102‐year period, 1906–2007. The comparison of time series revealed significant parallelism. Multiannual trends demonstrate decrease in transparency during the postwar period until 1983/1984. The trend ends with a steep decline of transparency after a series of four volcanic eruptions of Soufriere (1979), Saint Helens (1980), Alaid (1981), and El Chichón (1982). From 1984/1985 to 1990 the atmosphere remarkably restored its clarity, which almost reached again the level of the 1960s. Following the eruption of Mount Pinatubo (June 1991), there was the most significant reduction in column transparency of the postwar period. However, from the end of 1990s, the atmosphere in all considered locations is characterized with high values of transparency. The clearing of the atmosphere (from 1993) evidently indicates a decrease in the content of aerosol particles and, besides the decline of volcanic activity, may therefore be also traced to environmentally oriented changes in technology (pollution prevention), to general industrial and agricultural decline in the territory of the former USSR and Eastern Europe after deep political changes in 1991, and in part to migration of some industries out of Europe.

Enlightening Global Dimming and Brightening

“…Cloud cover changes effectively modulate SSR on an interannual basis, but their contribution to the detected longer-term (decadal) SSR trends is not always obvious (e.g., Qian et al 2006;Norris and Wild 2007). Dimming and brightening has also been observed under cloudless atmospheres at various locations, pointing to a prominent role of atmospheric aerosols (e.g., Wild et al 2005;Norris and Wild 2007;Sanchez-Lorenzo et al 2009;Ohvril et al 2009;Zerefos et al 2009). Aerosols can directly attenuate SSR by scattering and absorbing solar radiation (direct effect), or indirectly attenuate SSR through their ability to act as cloud condensation nuclei (CCN), thereby increasing cloud reflectivity and lifetime (first and second indirect effects) (e.g., Ramanathan et al 2001;Lohmann and Feichter 2005).…”

Long-term variability of aerosol optical thickness in Eastern Europe over 2001–2014 according to the measurements at the Moscow MSU MO AERONET site with additional cloud and NO<sub>2</sub> correction

“…The p 2 coefficient is widely used for assessing the variation of the transparency of the atmosphere (Ohvril et al, 2009). Using this characteristic, we estimated the integral optical thickness as τ = − ln (p 2 ).…”

Impact of aerosols and clouds on decadal trends in all-sky solar radiation over the Netherlands (1966–2015)

“…In the context of Europe there have been a considerable number of regional studies that focus on trends in global radiation and their attribution, such as in Germany (Liepert and Tegen, 2002;Liepert and Kukla, 1997;, in Germany and Switzerland combined (Ruckstuhl et al, 2008;Ruckstuhl and Norris, 2009;Ruckstuhl et al, 2010), in Estonia (Russak, 2009), in the general Baltic states (Ohvril et al, 2009), in Spain (Mateos et al, 2014), in Norway (Parding et al, 2014), northern Europe in general (Stjern et al, 2009) and in Italy (Manara et al, 2015). Even though there are regional differences, the summarized global or allsky radiation data from Europe combined display a minimum in [1984][1985] at the end of a "dimming" period with a subsequent return to higher values.…”