Abstract
Abstract. The build-up of pollutants to harmful levels can occur when meteorological conditions favour their production or accumulation near the surface. Such conditions can arise when a region experiences air stagnation. The link between European air stagnation, air pollution and the synoptic- to large-scale circulation is investigated in this article across all seasons and the 1979–2018 period. Dynamical indices identifying atmospheric blocking, Rossby wave breaking, subtropical ridges, and the North Atlantic eddy-driven and subtropical jets are used to describe the synoptic- to large-scale circulation as predictors in statistical models of air stagnation and pollutant variability. It is found that the large-scale circulation can explain approximately 60 % of the variance in monthly air stagnation, ozone and wintertime particulate matter (PM) in five distinct regions within Europe. The variance explained by the model does not vary strongly across regions and seasons, apart from for PM when the skill is highest in winter. However, the dynamical indices most related to air stagnation do depend on region and season. The blocking and Rossby wave breaking predictors tend to be the most important for describing air stagnation and pollutant variability in northern regions, whereas ridges and the subtropical jet are more important to the south. The demonstrated correspondence between air stagnation, pollution and the large-scale circulation can be used to assess the representation of stagnation in climate models, which is key for understanding how air stagnation and its associated climatic impacts may change in the future.
Highlights
Poor air quality poses one of the largest environmental threats to public health
We explore to what extent the large-scale circulation can explain the variability in air stagnation, followed by a comparison with that explained for the pollutants
As poor air quality is hazardous to human health (Pope III et al, 2002; Cohen et al, 2017), it is beneficial to understand the processes causing air stagnation
Summary
Poor air quality poses one of the largest environmental threats to public health. Long-term exposure to air pollutants such as particulate matter (PM) and ozone can cause severe cardiovascular and respiratory diseases and is responsible for between 200 000 and 400 000 premature deaths every year in Europe (World Health Organization, 2011; Giannadaki et al, 2016; European Environment Agency, 2020). The effect of stagnation on pollution can depend on season, with PM10 anomalies during stagnation in Europe lower in summer than in winter (Garrido-Perez et al, 2021), and region, with stagnation being a better predictor of summer ozone in central and southern Europe than in northern Europe (Garrido-Perez et al, 2019) Some of these studies are limited by the use of only one index to identify air stagnation. The results are compared for stagnation as defined in two additional ASIs and for direct estimates of concentrations of the pollutants PM2.5 and ozone This ensures that we can identify features of the synoptic- to large-scale flow that are truly important for air quality and not a feature of a particular ASI, as well as contributing to the debate on the usefulness of air stagnation as a proxy for air pollution events.
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