Compound climate events involving concurrent heatwaves and air pollution episodes represent a growing threat to public health. This study identifies the large-scale synoptic patterns most frequently associated with such events and their impact on summertime excess mortality in mainland Spain from 2015 to 2022. Using a combination of principal component analysis and cluster techniques applied to ERA5 reanalysis data, we classify 12 circulation types (CTs). Two of them, associated with Iberian thermal lows and upper-level ridges (CT1 and CT4), are linked to simultaneous anomalies in maximum temperature (+4–6 °C), ozone (+10– 25 μ g m −3 ) and PM 10 (+10– 40 μ g m −3 ), together accounting for 25% of summer days. To assess the impacts on mortality, the index M5d is proposed, representing the 5-day forward sum of all-cause deaths. CT1 and CT4 are associated with standardised M5d anomalies exceeding 1.5-2.0 standard deviations in several provinces, indicating a strong health response. Subtypes with Omega block configurations (e.g., CT1.3, CT4.4) show the highest efficiencies, with 70%–80% of days exceeding extreme thresholds for multiple variables and up to 50% efficiency in triggering excess mortality. These findings strengthen the scientific understanding of compound weather-health interactions in Southern Europe. • The main circulation types over the Iberian Peninsula during the summer are computed. • Upper-level ridges are related to high anomalies in temperature and air pollution. • Mortality excess takes place in two circulation types, accounting for 25% of days. • Extreme mortality occurs in patterns associated with compound events.
Garnés-Morales et al. (Sun,) studied this question.