The role of aerosol in altering North Atlantic atmospheric circulation in winter and its impact on air quality

• Published in: Atmospheric Chemistry and Physics
• Main Authors: PAUSATA Francesco, GAETANI Marco, MESSORI Gabriele, KLOSTER S., DENTENER Franciscus
• Language: English
• Published: COPERNICUS GESELLSCHAFT MBH 2015
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: https://publications.jrc.ec.europa.eu/repository/handle/JRC90921; https://doi.org/10.5194/acp-15-1725-2015

Numerical model scenarios of future climate depict a global increase in temperatures and changing precipitation patterns, driven by increasing greenhouse gas (GHG) concentrations. Aerosol concentrations also play an important role in altering Earth’s radiation budget and consequently surface temperature. Here, we use the general circulation aerosol model ECHAM5-HAM, coupled to a mixed layer ocean model, to investigate the impacts of future air pollution mitigation strategies in Europe on winter atmospheric circulation over the North Atlantic. We analyze the extreme case of a maximum feasible end-of-pipe reduction of aerosols in the near future (2030), in combination with increasing GHG concentrations. Our results show a more positive North Atlantic Oscillation (NAO) mean state in the near future, together with a significant eastward shift of the southern centre of action of the sea level pressure (SLP). Moreover, we show a significantly increased blocking frequency over the western Mediterranean. By separating the aerosol and GHG impacts, our study suggests that the aerosol abatement in the near future may be the primary driver of such circulation changes. All these concomitant modifications of the atmospheric circulation over the Euro-Atlantic sector lead to more stagnant weather conditions that favor air pollutant accumulation in the Mediterranean, especially in the western sector. These changes in atmospheric circulation should be included in future air pollution mitigation assessments. Our results suggest that an evaluation of NAO changes in individual climate model simulations will allow an objective assessment of the role of changes in wintertime circulation on future air quality. JRC.H.4 - Monitoring Agricultural Resources