Relation Between High-Pressure Blocking and Aerosol Concentrations in Southern Sweden

High-pressure blocking events are anticyclones that persist over a region for a long time. Such events prevent vertical mixing of air pollutants due to the subsidence inversion created by the anticyclone. This study investigates the relationship of aerosol concentrations during periods of high-pressure blocking events in southern Sweden for the rural location of Vavihill and the urban location of Malmö. A total of 226 high-pressure blocking events were identified in Vavihill and Malmö between 1995 and 2024. The high-pressure blocking events were sorted according to wind direction, season, and average pressure for further analysis. Moreover, to determine whether the frequency of blocking events affecting the region is changing, meteorological data from southern Sweden between 1946 and 2024 was analysed. Using Mann-Kendall statistics and standard deviations, the data showed a significant increase of PM2.5 for both locations during periods of high-pressure blocking. The trend indicated an accumulation of aerosols during the event in both locations. The investigation showed a stronger increase in PM2.5 with winds from eastern and central Europe, indicating advective transport of aerosols to the region. Local emissions most likely also played a role in the increasing PM2.5 levels, as suggested by Malmö generally having higher aerosol concentrations than Vavihill. High-pressure blocking events with a mean pressure above 1026 hPa showed the strongest increase in PM2.5. No long-term increase in the frequency of high-pressure blocking events was found in the region. The results from this study show how aerosol concentrations and air quality are highly dependent on atmospheric events in the region.