Recommended citation: Corredoira-Iglesias, M., González-Cámara, L. T., Eiras-Barca, J., Stojanovic, M.,Pérez-Alarcón, A.; Nieto, R., Gimeno, L. (2026). Physical drivers of the 2015 August moisture-modulated heatwave over the Iberian Peninsula: a Lagrangian analysis. 8th MedCLIVAR Conference. Limassol, Cyprus, 21-35 September 2026.

Abstract

In the current climate change context, extremes such as heatwaves are increasing in frequency, duration, and intensity. Thermal stress, which occurs when organisms are exposed to thermal conditions that surpass the limits of their thermoregulation, is intensifying worldwide, threatening human well-being and ecosystems. This issue can be exacerbated by atmospheric humidity, as it reduces the amount of heat dissipation by limiting the rate of sweat evaporation. However, the physical drivers underlying these extremes, including moisture and heat sources, have not been widely studied. Furthermore, the relative contributions of adiabatic, diabatic, and advective processes in the development of temperature anomalies have not been extensively investigated. Using the moisture-modulated heatwaves catalogue, broadly defined by the 99th percentile of the lethal heat stress index, a combined temperature and humidity metric for human heat stress, over 1979-2023, we selected an event that took place over the central, southern and eastern sectors of the Iberian Peninsula between 2 and 12 August 2015 as a case for detailed analysis within the dataset. To address the physical drivers of the designated event, we apply a Lagrangian approach to identify moisture and heat sources and decompose temperature anomalies into adiabatic, diabatic, and advective components, using the Lagrangian Atmospheric Moisture and Heat Tracking (LATTIN) tool. This allows us to develop a physically consistent synoptic framework and to assess the role of large-scale circulation and local surface-atmosphere feedbacks in the chosen 2015 episode and thus improve the physical understanding of moisture-modulated heatwave events in the Mediterranean regio