Solar and meteorological influences on seasonal atmospheric 7 Be in Europe for 1975 to 2018.

Assessing the transport of natural radionuclides in the atmosphere provides a powerful tool to study air mass circulation. Here, we investigated the seasonal atmospheric distribution of the naturally produced ⁷ Be in surface air over Europe between 40° N and 68° N during the period 1975-2018. The results suggest that the inter-annual variability of ⁷ Be reflects production rates of the radionuclide induced by solar modulation of cosmic rays. Further analysis of the meteorological influences indicates that the meteorological influences on ⁷ Be concentrations are geographically and seasonally dependent. We found that, in general, the tropopause pressure plays an important factor influencing ⁷ Be activity for winter and spring seasons while the sea level pressure and temperature are more dominant during summer and autumn seasons. The combination of tropospheric production rates and meteorological parameters explains 24%-79% variances of the seasonal ⁷ Be activity. We further applied a three-box model to study the influence of stratosphere-troposphere exchanges on ⁷ Be concentrations. The simulation supports that the seasonal cycle of ⁷ Be in Europe is controlled by two main factors: the changing height of the troposphere (seasonality of the tropopause height) and seasonal variations of the stratosphere-troposphere exchanges.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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