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

Abstract

In this paper we present the variation of 7 Be 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 7 Be in surface air. The mean annual activity concentration of 7 Be for the year 2009 was 6.0 mBq m −3 . The relative variability of 7 Be 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 7 Be 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 7 Be 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 7 Be in the atmosphere. The influence of precipitation on the 7 Be atmospheric concentration variability was approximately 10%, with greater the influence of rainfall events of low precipitation rate e.g. drizzling. *

Analysis of the influence of solar activity and atmospheric factors on 7Be air concentration by seasonal-trend decomposition

“…The correlation observed with the precipitations is supported by recent studies, which found a strong correlation between precipitations and 7 Be deposition fluxes (Chen et al, 2016;Zhang et al, 2016). In constrast, many studies have found a non-significant correlation between 7 Be row data and the total monthly precipitation per month (Azahra et al, 2004b;Ali et al, 2011;Pham et al, 2011;Kotsopoulou and Ioannidou, 2012).…”

“…Thus, the seasonal-trend decomposition reveals the strong influence of temperature on the seasonal variability of the 7 Be air concentration. Many studies have observed a negative correlation between 7 Be air concentration and relative humidity (Dueñas et al, 2009;Kotsopoulou and Ioannidou, 2012;Piñero-García and Ferro-García, 2012). However, in this study RH is positively correlated with the seasonal component ( = 0.60).…”

“…Solar activity has a direct relationship with the sunspot number and for this reason, this parameter is widely used to represent solar activity (Cannizzaro et al, 1995;Papastefanou and Ioannidou, 2004;Piñero-García and Ferro-García, 2013). Kotsopoulou and Ioannidou (2012) pointed out that solar activity is the dominant cause of the observed variation of galactic cosmic rays. Moreover, the geomagnetic field deflects incoming galactic cosmic rays toward the magnetic poles, so that the 7 Be production rate is much higher at high latitudes (Feely et al, 1989).…”

Identification of airborne radioactive spatial patterns in Europe – Feasibility study using Beryllium-7

“…Ioannidou et al, 2014), persistence of anticyclone conditions (no wet removal of aerosol particles) and higher convection (warm air transported upwards and cold air from the upper troposphere transported downwards), and the stratospheric intrusions during tropopause folding events govern the occurrence of maximum values, while, on the other hand, typical processes of the cold period, such as high relative humidity conditions, resulting in increased particle sizes of atmospheric aerosols, and so, higher scavenging rate of aerosols, or the occurrence of strong rainfall events can cause the decreased activity concentrations in the surface air (Kotsopoulou and Ioannidou, 2012).…”

Forecasting 7 BE concentrations in surface air using time series analysis

“…Be is a cosmogenic radionuclide formed by spallation reactions of light atmospheric nuclei (such as carbon, nitrogen and oxygen) with very high-energy protons and neutrons of the primary cosmic rays(Lal et al, 1958;Bruninx, 1961). Most7 Be production (∼70%) occurs in the stratosphere and the remainder (∼30%) is produced in the troposphere, so that the7 Be production rate is altitude-dependent(Feely et al, 1989;Baeza et al, 1996;Kotsopoulou & Ioannidou, 2012).…”