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Given its proximity to northern Africa, southern Spain is regularly affected by high-altitude African intrusions. This determines a well-defined wind dynamics at surface levels. Although this weather event—mainly recorded in spring and summer—coincides with the flowering season of many wind pollinated species, its potential influence on long term airborne pollen transport has been not investigated in detail. We analyse their influence on olive pollen transport at surface level in south Spain. Daily and bi-hourly olive pollen data from 2010 to 2015, recorded at two sites 150 km apart, Málaga (coast) and Córdoba (inland), were analysed together with 1) air masses at 300 m above ground level (m.a.g.l.), 2) surface wind direction and 3) surface wind speed over the same period. Air masses at 3000 m.a.g.l. were used to identify the periods under the influence of African intrusions. The combined analysis has enabled the identification of different pollen patterns and source contributions. In Málaga, hourly pollen peaks were recorded during the early morning coinciding with the arrival of north-westerly winds (developing sea-land breezes), with a minimal impact of local pollen sources; in Córdoba, by contrast, pollen concentrations reflected the joint contribution of local and long term sources, being the maximum concentrations associated with the arrival of southerly air masses in the afternoon. These results help to understand the potential distant sources and back-trajectories of olive pollen detected. In our case pollen from sources located at the west-northwest areas in the case of Malaga, and from the south in Cordoba. These results reinforce the idea that combined studies between synoptic meteorological and aerobiological data together with different atmospheric height air masses data, offer us a better explanation and understanding of the behaviour and the potential sources of recorded airborne data in a given place. [ABSTRACT FROM AUTHOR]

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: Located in the southwest of the Iberian Peninsula, the Guadalquivir valley is a site of frequent problems related to air pollution. The atmospheric dynamics of this region is poorly characterised but is fundamental to understanding the chemical and photochemical processes that contribute to the pollution problems. In this work, the atmospheric mesoscale Weather Research and Forecasting (WRF-ARW) model was used to study the horizontal and vertical development of the two sea–land breeze patterns (pure and non-pure) that are identified in the coastal area as being responsible for many of the air pollution events. In addition, data from five meteorological stations within the valley were used to validate and compare the model results. The FNL archives were used to define the initial and boundary conditions of the model. Four domains with a grid resolution of 81, 27, 9 and 3km and 40 sigma pressure levels in each domain were defined. The Medium Range and Forecast (MRF) parameterisation scheme was used with new values for both the bulk critical Richardson number and the coefficient of proportionality. This new configuration was obtained from the sensitivity exercises. Several periods were modelled for both breeze patterns, focusing on the wind, the potential temperatures and the specific humidity fields. For the pure breeze, the horizontal movement along the valley was conditioned by the arrival of a Mediterranean flow in the Guadalquivir valley that limits the horizontal extension of the breeze to 20–40km inland. In contrast, the non-pure pattern was only identified in the coastal area; although motivated by the entrance of southwestern flows, a marine air mass transport along the valley was detected and reached inland areas located approximately 200km from the coast line. In both cases, the model results indicated the formation of a thermal internal boundary layer with a vertical development of less than 500m for the pure sea breeze while for the non-pure breeze can reach a vertical extension of 1km. In the case of the non-pure pattern, the model forecast for the Atmospheric Boundary Layer (ABL) height distribution along the valley revealed a homogeneous pattern related to the entrance of the southwestern flows, in contrast with the clear division of the valley observed for the pure pattern motivated by the arrival of Mediterranean flows. [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]

Abstract: Massive amounts of anthropogenic radionuclides were released from the nuclear reactors located in Fukushima (northeastern Japan) between 12 and 16 March 2011 following the earthquake and tsunami. Ground level air radioactivity was monitored around the globe immediately after the Fukushima accident. This global effort provided a unique opportunity to trace the surface air mass movement at different sites in the Northern Hemisphere. Based on surface air radioactivity measurements around the globe and the air mass backward trajectory analysis of the Fukushima radioactive plume at various places in the Northern Hemisphere by employing the Hybrid Single-Particle Lagrangian Integrated Trajectory model, we show for the first time, that the uninterrupted complete revolution of the mid-latitude Surface Westerlies took place in less than 21days, with an average zonal velocity of>60km/h. The position and circulation time scale of Surface Westerlies are of wide interest to a large number of global researchers including meteorologists, atmospheric researchers and global climate modellers. [Copyright &y& Elsevier]

Abstract: On 12 and 13 August 2006, an exceptional air pollution event occurred in the southwest of the Iberian Peninsula (western Andalusia). High concentrations of surface ozone, CO and PM10 were registered at several air quality stations, in some cases reaching record values. During the late afternoon and evening of these two dates, the information and alert thresholds of surface ozone at coastal stations were exceeded, with peaks of 270 μg m−3. Concentrations of CO and PM10 reached 1800 μg m−3 and 240 μg m−3. Surface meteorological observations, back trajectories computed with the HYSPLIT model and wind and specific humidity fields from the meso-meteorological WRF-ARW model have all been used to gain an understanding of the origin of this event. The results indicate that this event was caused by the long-range transport of air masses from the wildfires that had occurred in the northwest of the Iberian Peninsula (Galicia and northern Portugal) during the first two weeks of August 2006. Air masses loaded with pollutants were transported approximately 1000 km from north to south, over Portugal and the Atlantic Ocean, to reach the southwestern Iberian Peninsula, with the consequent negative high impact on the air quality of this region. [Copyright &y& Elsevier]

Abstract: High activity concentrations of several man-made radionuclides (such as 131I, 132I, 132Te, 134Cs and 137Cs) have been detected along the Iberian Peninsula from March 28th to April 7th 2011. The analysis of back-trajectories of air masses allowed us to demonstrate that the levels of manmade radionuclide activity concentrations in the southwest of the Iberian Peninsula come from the accident produced in the nuclear power plant of Fukushima. The pathway followed by the radioactive plume from Fukushima into Huelva (southwest of the Iberian Peninsula) was deduced through back-trajectories analysis, and this fact was also verified by the activity concentrations measured of those radionuclides reported in places crossed by this radioactive cloud. In fact, activity concentrations reported by E.P.A., and by IAEA, in several places of Japan, Pacific Ocean and United States of America are according to the expected ones from the air mass trajectory arriving at Huelva province. [Copyright &y& Elsevier]

The contribution of 220 Rn is usually negligible compared to that of 222 Rn: its very short half-life makes escape from its source site within the rock very unlikely and it never has time enough to filtrate through the ground and through cracks in the floors or cellar walls to reach living quarters. This however becomes untrue if walls built with 232 Th-rich materials are present: then sizeable amounts of thoron may be detected in the closed areas bounded by those walls. This is the case for many dwellings in central Italy, and the town of Bolsena (northern Latium) is presented as a case study. A typical building of the area, entirely constructed with tuff blocks, is investigated and the annual dose rates calculated for varying distances from the wall. Thoron concentration was found to decrease with a relaxation length of 13 cm. Thoron was found to pose a significant risk. The rate of air exchange was found to produce little effect. Wall plastering acts as a filter: thoron diffuses through it but a HVL of less than 1 cm was found to prevail. [ABSTRACT FROM AUTHOR]

Relationships between the beryllium-7 activity concentrations in surface air and meteorological parameters (temperature, atmospheric pressure, and precipitation), teleconnection indices (Arctic Oscillation, North Atlantic Oscillation, and Scandinavian pattern) and number of sunspots are investigated using two multivariate statistical techniques: hierarchical cluster and factor analysis. The beryllium-7 surface measurements over 1995–2011, at four sampling sites located in the Scandinavian Peninsula, are obtained from the Radioactivity Environmental Monitoring Database. In all sites, the statistical analyses show that the beryllium-7 concentrations are strongly linked to temperature. Although the beryllium-7 surface concentration exhibits the well-characterised spring/summer maximum, our study shows that extremely high beryllium-7 concentrations, defined as the values exceeding the 90 th percentile in the data records for each site, also occur over the October–March period. Two types of autumn/winter extremes are distinguished: type-1 when the number of extremes in a given month is less than three, and type-2 when at least three extremes occur in a month. Factor analysis performed for these autumn/winter events shows a weaker effect of temperature and a stronger impact of the transport and production signal on the beryllium-7 concentrations. Further, the majority of the type-2 extremes are associated with a very high monthly Scandinavian teleconnection index. The type-2 extremes that occurred in January, February and March are also linked to sudden stratospheric warmings of the Arctic vortex. Our results indicate that the Scandinavian teleconnection index might be a good indicator of the meteorological conditions facilitating extremely high beryllium-7 surface concentrations over Scandinavia during autumn and winter. [ABSTRACT FROM AUTHOR]