Impact of the North Atlantic Oscillation on European aerosol ground levels through local processes: a seasonal model-based assessment using fixed anthropogenic emissions

S Jerez,J P Montávez,R M Trigo,P Jimenez-Guerrero

doi:10.5194/acp-13-11195-2013

S Jerez, J P Montávez + Show 2 more

Open Access

https://doi.org/10.5194/acp-13-11195-2013

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Abstract

Abstract. The North Atlantic Oscillation (NAO) controls a large amount of the European climate variability with asymmetric impacts in both time and space. Here we investigate how the NAO impact on the local atmospheric processes (disregarding the NAO impact on the large inter-continental transport mechanisms) influences the levels of various aerosol species using simulated data under constant emissions, which are fixed to the 2005 levels in order to avoid anthropogenic-induced signals. In particular, we analyze interannual variations at the seasonal timescale and focus on the ground-level. The results show that positive NAO phases favor increased aerosol concentrations in southern (northern) regions during winter (summer), while negative NAO phases enhance them in northern (southern) regions during winter (summer). The underlying processes are clearly related to the NAO impact on precipitation and wind, as they act to clean the atmosphere through removal and dispersion processes, and to the NAO impact on the radiation balance (i.e., cloudiness) as it affects the biogenic emitting activity and on the oxidative capacity of the atmosphere. Differences for all the species studied (natural inert, secondary inorganic and organic aerosols) are up to 5 μg m−3, reaching 10 and 20 μg m−3 for PM10 and PM2.5 respectively, which represents variations of about 20–40% in their mean levels between opposite NAO phases.

Highlights

Air pollution is a major environmental and health problem affecting industrialized and developing countries around the world
This Section does not intend to provide novel insights, but essentially to evaluate the ability of our climate simulation to simulate the extensively reported North Atlantic Oscillation (NAO) impact on the European atmospheric conditions. This fulfills two relevant requirements, namely to (1) guarantee that it is effectively able to reproduce the known NAO impact on the European climate, and (2) provide an appropriate context for the interpretation of the following results of the NAO impact on aerosol concentrations, since the analysis is focused on those variables driving air pollution levels
NAO+ (NAO−) promotes a windy westerly flow in northern Europe (Fig. 3a, c), with the largest significant differences in the wind speed appearing northward in the western sector of the domain (Fig. 3c)

Summary

Introduction

Air pollution is a major environmental and health problem affecting industrialized and developing countries around the world. Main detrimental consequences of the exposure of humans to photochemical and particulate matter pollution include respiratory difficulties, especially for sensitive people (Pope and Dockery, 2006). The most serious problems in Europe are related with particulate matter with a diameter of less than 10 μm (PM10), nitrogen dioxide and ozone. In this sense, worldwide epidemiological studies show a consistent increase in cardiac and respiratory morbidity and mortality from exposure to air pollution (e.g., Pope et al, 2009). In order to anticipate when and why episodes of air pollution arise and how they can be abated, reliable estimations of air pollution levels and a better understanding of the chemicophysical processes behind them are crucial

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