Analysis of the influence of solar activity and atmospheric factors on 7Be air concentration by seasonal-trend decomposition

Be-7 air concentrations were measured at the Universitat Politecnica de Valencia campus (in the east of Spain) during the period 2007-2014. The mean values of monthly Be-7 concentrations ranged from 2.65 to 8.11 mBq/m(3), showing significant intra and interannual variability. A seasonal-trend decomposition methodology was applied to identify the trend-cycle, seasonal and irregular components of the Be-7 time series. The decomposition model makes it possible to estimate the influence of solar activity and atmospheric factors on the independent components, in order to find the different sources of Be-7 variability. The results show that solar activity is a factor with a high inverse influence on the trend-cycle pattern of Be-7 variability. Solar radiation, temperature and relative humidity are positive influential factors on the seasonal Be-7 variation with a regular pattern over the years. Finally, the irregular component presents a significant negative correlation with precipitation and wind speed parameters, which have an irregular behavior over the years and seasons. (C) 2016 Elsevier Ltd. All rights reserved.