Connection between Weather Types and Air Pollution Levels: A 19-Year Study in Nine EMEP Stations in Spain.

This study focuses on the analysis of the distribution, both spatial and temporal, of the PM (particulate matter with a diameter of 10 µm or less) concentrations recorded in nine EMEP (European Monitoring and Evaluation Programme) background stations distributed throughout mainland Spain between 2001 and 2019. A study of hierarchical clusters was used to classify the stations into three main groups with similarities in yearly concentrations: GC (coastal location), GNC (north-central location), and GSE (southeastern location). The highest PM concentrations were registered in summer. Annual evolution showed statistically significant decreasing trends in PM concentration in all the stations covering a range from -0.21 to -0.50 µg m/year for Barcarrota and Víznar, respectively. Through the Lamb classification, the weather types were defined during the study period, and those associated with high levels of pollution were identified. Finally, the values exceeding the limits established by the legislation were analyzed for every station assessed in the study.