⁷Be atmospheric concentration at mid latitudes (40°N) during a year of solar minimum

Aristotle University of Thessaloniki, Physics Department Nuclear Physics & Elementary Particle Physics Division Thessaloniki 54124, Greece

^* E-mail: anta@physics.auth.gr

Abstract

In this paper we present the variation of ⁷Be concentration in the surface air of Thessaloniki, Greece (40°62′N, 22°95′E) over the year 2009, a year of a deep solar minimum, and, as a consequence, a year of maximum concentration of ⁷Be in surface air. The mean annual activity concentration of ⁷Be for the year 2009 was 6.0 mBq m⁻³. The relative variability of ⁷Be surface concentration related to the solar cycle was calculated to be deviated by about 20% from maximum to mean. A positive correlation (R = 0.97) was revealed between the activity of ⁷Be and the temperature T (°C), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, that make descend air masses enriched in ⁷Be down to the surface layer. The anticorrelation (R = –0.65) with RH% is due to intense condensation during high relative humidity conditions, which results in increased aerosol particle sizes and as a consequence in higher scavenging rate of aerosols and lower concentration of ⁷Be in the atmosphere. The influence of precipitation on the ⁷Be atmospheric concentration variability was approximately 10%, with greater the influence of rainfall events of low precipitation rate e.g. drizzling.