Atmos. Chem. Phys. Discuss., 12, 10815-10843, 2012
© Author(s) 2012. This work is distributed
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Decadal variations in estimated surface solar radiation over Switzerland since the late 19th century
A. Sanchez-Lorenzo and M. Wild
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland

Abstract. Our knowledge on trends in surface solar radiation (SSR) involves uncertainties due to the scarcity of long-term time series of SSR, especially with records before the second half of the 20th century. Here we study the trends of all-sky SSR from 1885 to 2010 in Switzerland, which have been estimated using a homogenous dataset of sunshine duration series. This variable is shown to be a useful proxy data of all-sky SSR, which can help to solve some of the current open issues in the dimming/brightening phenomenon. Unlike the second half of the 20th century that is characterized also in Switzerland by a dimming from the 1950s to the 1980s and a subsequent brightening, all-sky SSR has been fairly stable with little variations in the first half of the 20th century. Cloud cover changes seem to explain the major part of the decadal variability observed in all-sky SSR, at least until the 1970s; at this point, a discrepancy in the sign of the trend is visible in the series. Finally, an attempt to estimate SSR series for clear-sky conditions, based also on sunshine duration records since the 1930s, has been made for the first time. The mean clear-sky SSR series shows no relevant changes between the 1930s to the 1950s, then a decrease from 1960s to 1970s, and ends with a strong increase from the 1980s up to the present. During the last three decades the estimated clear-sky SSR trends reported in this study are in line with previous findings over Switzerland based on direct radiative flux measurements. Equally, the clear signal of the El Chichón and Pinatubo volcanic eruption visible in the estimated clear-sky SRR records further demonstrates its potential to infer aerosol-induced radiation changes from sunshine duration observations.

Citation: Sanchez-Lorenzo, A. and Wild, M.: Decadal variations in estimated surface solar radiation over Switzerland since the late 19th century, Atmos. Chem. Phys. Discuss., 12, 10815-10843, doi:10.5194/acpd-12-10815-2012, 2012.
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