Time lag between the tropopause height and the levels of ⁷Be concentration in near surface air

¹ Aristotle University of Thessaloniki, Physics Department Nuclear Physics & Elementary Particle Physics Division Thessaloniki 54124, Greece
² Aristotle University of Thessaloniki, Physics Department Applied and Environmental Physics Division Laboratory of Atmospheric Physics - Thessaloniki 54124, Greece

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

Abstract

The concentration of ⁷Be at near surface air has been determined over 2009, a year of a deep solar minimum, in the region of Thessaloniki, Greece at 40°62′ N, 22°95'E. In geomagnetic latitudes over 40° N, the elevation of the tropopause during the warm summer months and the vertical exchange of air masses within the troposphere cause greater mixture of the air masses resulting in higher concentration levels for ⁷Be in surface air. The positive correlation between the monthly activity concentration of ⁷Be and the tropopause height (0.94, p < 0.0001), and also between ⁷Be concentration and the temperature T (°C) (R = 0.97, p < 0.001), confirm that the increased rate of vertical transport within the troposphere, especially during warmer summer months, has as a result the descent to surface of air masses enriched in ⁷Be. However, the ⁷Be concentration levels in near surface air are not expected to respond immediately to the change of elevation of the tropopause. It was found that there's a time lag of ~ 3 days between the change in the daily surface concentrations of ⁷Be the change in the elevation of the tropopause.