Aerosols under heatwaves: Interactions between pollution and heatwave extremes

Air pollution frequently occurs in urban areas, often associated with heatwaves, especially during the warmer seasons, which produce an added risk to public health. We have analysed multi-decadal aerosol and meteorological data over the Tirana metropolitan region (1980-2024) to quantify how aerosol load in terms of aerosol optical thickness (AOT) responds during heatwave events. Using ERA5 reanalysis, MERRA-2 aerosol fields, and MODIS AOT products, we identify heatwaves with a daily Tmax exceeding the 90th percentile (1981 -2010 baseline), aggregate event metrics, and compute synoptic composites. Heatwaves are consistently associated with positive aerosol anomalies: mean AOT increases of ≈+0.10 and modelled PM2.5 increases of 10-20 μg m−3 during event days. Multivariate analyses suggest that heatwave principal parameters explain a significant portion of the total aerosol variation (r ≈ 0.48 for event peaks). Several coincidental occurrences of both extremes have been identified, and a special case is further analysed. These results highlight the importance of analysing heat and air quality extremes as coupled phenomena and using integrated warning and mitigation strategies in the areas at risk, such as urbanised and industrialised areas. .