Long-term series of surface solar radiation at Athens, Greece

We present a long-term series of solar surface radiation (SSR) for the city of Athens, Greece. The SSR measurements were performed from 1953 to 2012, and before that (1900–1952) sunshine duration (SD) records have been used in order to reconstruct monthly SSR. Analysis from the whole dataset (1900–2012) mainly showed: a decrease of 2.9 % per decade in SSR from 1910 to 1940 assuming a linear change in SSR. For the dimming period (1955–1980), a −2 % change per decade has been observed, that matches various European long-term SSR measurement related studies. This percentage for Athens is in the lower limit, compared to other studies for the Mediterranean area. For the brightening period (1980–2012) we have calculated a +1.5 % per decade which is also in the lower limit of the reported positive changes in SSR around Europe. Comparing the 30-year periods (1954–1983 and 1983–2012) we have found a difference of 4.5 %. The difference was observed for all seasons except winter. Using an analysis of SSR calculations of all sky and clear sky (cloudless) conditions/days, we report that most of the observed changes in SSR after 1954 can be attributed partly to cloudiness and mostly to aerosol load changes.