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The long-term monitoring of the cosmogenic 7Be activity concentrations has been used to better understand the influence of large-scale atmospheric circulation dynamics in the troposphere. With an aim, this study analyzes weekly 7Be data from 15 sampling stations in Europe over 2005–2014. We first define peak (or extremely high) events in each station as those activity concentrations above the 90th percentile, and then investigate their temporal and spatial variability. These events are most frequent in the spring and summer seasons, with a notable latitudinal variability in their number. Next, we use back-trajectory cluster analysis to identify the main advection pathways associated with these high concentrations. To achieve this, persistent periods, i.e., sampling periods over which at least 60% of the calculated backward trajectories arriving at a given site correspond to the same airflow pattern, are taken as reference. This method reveals large differences in the association between the airflow patterns observed at different stations in connection with the 7Be peaks. A comparison between stations shows no clear spatial pattern, which suggests a further influence of mesoscale/local physical processes on the surface 7Be activity concentrations. Finally, the main airflow pattern at each sampling site and the associated 7Be peaks, are related to the main teleconnection patterns of large scale and regional climate variability in Europe: North Atlantic Oscillation, Arctic Oscillation, East Atlantic, East Atlantic/Western Russia, Scandinavian pattern and Western Mediterranean Oscillation. The results point out the connection between the negative phases of NAO and We-MO, and the positive phase of EA with the spatial and temporal variability and occurrence of the 7Be peak activity concentrations. These results show a latitudinal division between northern and southern sites, with similar influence of teleconnection patterns, while those located in the central part of Europe present larger variability in the impact of teleconnection patterns. [Display omitted] • Evaluate the temporal and spatial variability of the extreme 7Be activity concentrations in Europe (2005–2014). • Evidence differences in airflow patterns associated with extreme 7Be concentrations in Europe. • Reveal the influence of the main teleconnection patterns on extreme 7Be concentrations. • Identify latitudinal differences according to extreme 7Be activity concentrations and meteorological factors. [ABSTRACT FROM AUTHOR]

Abstract: 210Pb and 7Be activity concentrations in surface air and in bulk deposition have been measured from November 2009 to December 2011 along the Gulf of Cadiz (Southwest of Spain). This area presents mesoscale variations in its meteorological conditions, with influence of air masses with different origins: maritime, either from the Atlantic Ocean or the Mediterranean Sea and continental, from Iberian Peninsula and north of Africa, which make possible this region to be suitable to analyse the mesoscale spatial and temporal variations of atmospheric compounds. The objective of this study is to determine if there are differences in 210Pb and 7Be activity concentrations in surface air and in bulk deposition at the mesoscale level in this complex area of southwestern Iberian Peninsula taking as reference two sites of the same geographical area but influenced by different meteorological conditions. The temporal evolution pattern of PM10 was different for each site (no correlation between both series was found), but the PM10 average concentrations were similar for both locations (differences were not found at 0.05 significance level). On the other hand, the temporal evolution of 7Be and 210Pb activity concentrations in surface air show a good correlation between both sites, indicating this fact a similar behaviour of these radionuclides in the area. Finally, for each location a strong correlation between 210Pb and 7Be depositional fluxes was also observed, showing that wet deposition plays a key role in the deposition fluxes of both radionuclides. The averages depositional fluxes for 7Be and 210Pb are 750 Bq m−2 y−1 and 60 Bq m−2 y−1 in both locations, respectively. This set of results allows to determine that both radionuclides (7Be and 210Pb) present similar atmospheric behaviours, although with mesoscale variations in the magnitude of the values along the entire southern coast of the Iberian Peninsula. [Copyright &y& Elsevier]

Abstract: During a seven-year period (April 2004–July 2011), the 210Pb and 7Be activity concentrations in surface air were determined at El Arenosillo, located on the coastline of the southwestern Iberian Peninsula. The 210Pb and 7Be activity concentrations have been classified in four ranges according to the values of percentiles, 0–P10 (lowest concentrations), P10–P50 (intermediate concentrations), P50–P90 (high concentrations), and P90–Maximum (peaks of concentrations). The computation of both backward trajectories and cluster techniques has been used for identifying the types of air masses that arrive at the sampling station for each range of 210Pb and 7Be activity concentrations. Meteorological parameters, such as the wind roses and daily cycles of specific and relative humidity, and the potential temperature have been calculated (or measured) for each one of the sampling periods and grouped according to the ranges of 210Pb and 7Be activity concentrations. The results indicate that different synoptic patterns are associated with different 210Pb and 7Be activities in this area, which indicates the differences between the arrival of maritime and continental air masses based on the 210Pb and 7Be activities. In addition, the study on the evolution of air masses from the lowest and highest ranges of 7Be/210Pb confirms that both radionuclides can be used as two independent atmospheric transport markers. [Copyright &y& Elsevier]

The components and the periodicity characterising airborne 7Be monthly concentration collected in Granada (SE Spain) between 2000 and 2018 are studied. These 19 years of measurements are particularly significant for the 7Be analysis as they cover the complete 24th solar cycle, 2008–2018. A Time Series Decomposition (TSD) technique has been applied to determine the different components present in the dataset: the trend, seasonal and irregular components. Then, the atmospheric parameters (Precipitation (Pp), Relative Humidity (RH), Temperature (Temp), Wind speed (WS), Total Cloudiness (TC), Low Cloudiness (LC)), teleconnection indices and the solar activity (Sun Spot Number, SSN) were used to justify the variability of each component. SSN and the teleconnection indices (Western Mediterranean Oscillation (WeMO), Atlantic Multidecadal Oscillation (AMO) and Quasi Biennial Oscillation (QBO)) are found to have a major impact on the trend component of 7Be. In turn, all the atmospheric parameters were found to have strong impact on the seasonal component. In order to observe the change in the impact of the parameters from the 24th solar cycle (from 2008 to 2018) to the complete time series (starting in 2000), the comparison between the two periods has been carried out. The results show that, over the 24th solar cycle, the SSN impacted predominantly on the trend component, whereas atmospheric parameters showed a slightly higher impact on the seasonal component. In addition, some atmospheric factors (Temp, RH, Pp, TC, LC) appeared to partially affect the irregular component. The analysis of the two phases of the 24th solar cycle shows that the influence of SSN is higher during the descending phase than during the ascending one. This behaviour is opposed to the one found for the 23rd solar cycle, which clarifies the special characteristics of the 24th cycle. Besides that, the Continuous Wavelet Transform (CWT) analysis was applied in order to extract the possible periodicities characterising 7Be data. The analysis revealed three sets of periodicities. Then, the Wavelet Coherence Analysis (WCA) method was particularly useful to study coherences between 7Be data and teleconnection indices. The 7Be concentrations in the large period (11–14 years) detected by CWT was found to be mainly modulated by WeMO, AMO and QBO, while the NAO modulates the smaller periods. • A time series decomposition technique was applied to 19 years of monthly 7Be data in Granada. • 11 different parameters were used to justify each component for all the period and for the 24th solar cycle. • Study the two phases of 23rd and 24th solar cycles shows the difference between their impacts on 7Be in air. • A set of 7Be periodicities was determined using the wavelet transform analysis. • The 7Be periodicities were found to be modulated by climatic indices phenomena. [ABSTRACT FROM AUTHOR]