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

Abstract

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 ⁷Be 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 ⁷Be 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 ⁷Be concentrations are geographically and seasonally dependent. We found that, in general, the tropopause pressure plays an important factor influencing ⁷Be 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 ⁷Be activity. We further applied a three-box model to study the influence of stratosphere-troposphere exchanges on ⁷Be concentrations. The simulation supports that the seasonal cycle of ⁷Be 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.

Keywords: Beryllium-7; Meteorological influences; Solar modulation; Stepwise regression; Stratospheric intrusion; Three-box model.