Abstract
The atmospheric concentration of persistent organic pollutants (and of polycyclic aromatic hydrocarbons, PAHs, in particular) is closely related to climate change and climatic fluctuations, which are likely to influence contaminant’s transport pathways and transfer processes. Predicting how climate variability alters PAHs concentrations in the atmosphere still poses an exceptional challenge. In this sense, the main objective of this contribution is to assess the relationship between the North Atlantic Oscillation (NAO) index and the mean concentration of benzo[a]pyrene (BaP, the most studied PAH congener) in a domain covering Europe, with an emphasis on the effect of regional-scale processes. A numerical simulation for a present climate period of 30 years was performed using a regional chemistry transport model with a 25 km spatial resolution (horizontal), higher than those commonly applied. The results show an important seasonal behaviour, with a remarkable spatial pattern of difference between the north and the south of the domain. In winter, higher BaP ground levels are found during the NAO+ phase for the Mediterranean basin, while the spatial pattern of this feature (higher BaP levels during NAO+ phases) moves northwards in summer. These results show deviations up to and sometimes over 100% in the BaP mean concentrations, but statistically significant signals (p<0.1) of lower changes (20–40% variations in the signal) are found for the north of the domain in winter and for the south in summer.
Highlights
The North Atlantic Oscillation (NAO) is the normalised sea level pressure difference between the Azorean high and the Icelandic low, which is responsible for a considerable share of variability in European climate
(driving the CHIMERE run) to simulate the extensively reported NAO impact on the European atmospheric conditions. As this analysis was widely conducted by Jerez et al (2013a), we mainly summarize this work to give the reader an appropriate context for the interpretation of the NAO impact on BaP concentrations, since the analysis is focused on those variables driving air pollution levels
When the concentrations of BaP during NAO+ minus NAO− phases are estimated over Europe, strongly marked effects can be perceived temporally and spatially, namely yielding differences between seasons and north and south, respectively
Summary
The North Atlantic Oscillation (NAO) is the normalised sea level pressure difference between the Azorean high and the Icelandic low, which is responsible for a considerable share of variability in European climate. The impacts of the NAO include a meridional sea level pressure gradient in the North Atlantic, with positive phases characterised by an intense north–south gradient and negative phases when the gradient decreases (Hurrell 1995). The influxes of dust from the Sahara desert towards the Atlantic and Mediterranean (Moulin et al 1997), and photochemical processes that have an effect on the transport of atmospheric contaminants from North America to Europe (Li et al 2002).
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