Distribution of ⁷Be in surface air of Europe

This study deals with long-term (span over three decades, 1972-2003) distribution of the cosmogenic isotope ⁷Be in surface air at 5 stations in Europe, extending from latitude 47°N to 68°N. The results suggest annual variability in all the data sets as well as a decrease in average ⁷Be activity with increasing latitude. Furthermore, a 9-10-year cyclical pattern is observed in the ⁷Be distribution, which is anticorrelated with the solar activity cycle. Our data also indicate a dynamic range of ⁷Be activity for each solar cycle and phase (maximum or minimum) which is higher at the middle compared to high-latitude regions. Additionally, about 10-20% relative deviation is observed in ⁷Be activity during solar maxima and minima compared to the total average ⁷Be. This feature indicates that some deviation in the worldwide ⁷Be activity data may relate to their acquisition, with respect to which part of a solar cycle they have been collected in (time span) and at which latitudinal spread. Estimate of ⁷Be flux onto European surface boundary layer vary from 0.4 to 0.9 × 1 0¹⁰ atoms m^{- 2} yr^{- 1} which is strongly latitude dependent and our average value is comparable to the ∼ 0.7 - 0.8 × 1 0¹⁰ atoms m^{- 2} yr^{- 1} across ocean and land.