Vertical Variability of Temperature and Moisture in a Compound Dust-Heatwave Scenario at South-Western Iberian Peninsula: Implications for Surface Thermal Stress and CCN Predictions

A comprehensive analysis of the vertical thermodynamic structure during a compound dust–heatwave (dust–HW) event over the south-western Iberian Peninsula is presented in this study to investigate potential impacts on surface heat stress and cloud condensation nuclei (CCN) conditions. Lidar observations were performed at two dust-influenced stations, Évora (Portugal) and El Arenosillo/Huelva (Spain), during the intense June 2022 Saharan dust intrusion associated with a persistent HW event. The dust intrusion was characterized by high aerosol optical depths (up to ~1) and long duration (8 days). The dust layer extended from the surface up to approximately 6–7 km height, with the highest concentrations detected below 3–4 km. Similar temporal and vertical thermodynamic patterns were observed at both stations, indicating regional-scale consistency during the compound dust–HW event. Near-surface temperatures increased significantly during the dusty period compared with surrounding non-dusty days, suggesting enhanced surface heat-stress conditions under concurrent dust–HW environments. A distinct vertical thermodynamic structure was also identified, with air temperature (AT) increasing within the main dust layer, while relative humidity (RH) decreased below and increased above the layer where the highest dust concentrations were detected (3–4 km). Additional ERA5 vertical velocity diagnostics revealed ascending-motion signatures coinciding with RH-enhanced layers above the main dust intrusion, supporting dynamically consistent conditions for upward moisture transport during the event. Under these RH-enriched and ascending-motion conditions, retrieved CCN concentration estimates suggested potentially enhanced CCN activation environments above the main dust layer under moderate supersaturation scenarios. Overall, the results provide observational evidence consistent with a coupling among dust transport, thermodynamic variability, and CCN-related processes during HW conditions. These findings highlight the importance of understanding concurrent dust–HW environments in dust-influenced regions under projected future HW intensification associated with climate change, and their connection with aerosol-cloud interactions (ACI).