Association between Prevailing Circulation Patterns and Coarse Particles in Portugal

Abstract

Air pollution is one of the major environmental concerns today, with high socio-economic and public health impacts, which are expected to worsen in the future due to anthropogenic warming. Among the toxic agents present in the atmosphere, coarse particles (PM10 and PM2.5) are some of the most harmful for human health and the environment. Therefore, the study of these particles and their association with meteorological constraining factors is of utmost importance. The aim of this study is to analyze the circulation weather types (CWT) affecting PM10 and PM2.5 concentrations measured at background monitoring stations in Portugal between 2006 and 2018. PM10 and PM2.5 were analyzed in terms of their intra-annual and inter-annual variability, their relations with CWT and the characteristics of two major extreme events over Portugal. The analysis of the extreme events relied on both background stations and through the near-real time data from Copernicus Atmosphere Monitoring Service (CAMS) outputs. The inter-annual assessment showed a decrease in concentrations over the studied years, mainly for PM10. Intra-annual assessment pointed to higher concentrations during winter months. Higher PM concentrations were mostly associated with CWTs with easterly or southerly components, characterized by low frequency of rainfall and advection of dry air masses. The two analyzed extreme events, associated with mega wildfires (15–17 October 2017) and dust intrusion (1–10 August 2018) were analyzed in more detail. Prominent southerly and easterly circulations were observed during the onset and peak of the events, which then later decayed due to the change to maritime flows (westerly and northerly circulation types) which dispersed the particles.