Author(s): Luis Angel Espinosa; Maria Manuela Portela

Linked Author(s): Luis Angel Espinosa

Keywords: Exceptional Precipitation; Severity Heat Map; ERA5-Land; Climate Change

Abstract: This study examines the spatial and temporal dynamics of exceptional precipitation in Portugal over 42 hydrological years (1981/1982–2022/2023) using ERA5-Land daily precipitation data. The research focuses on evaluating changes in the frequency and intensity of exceptional rainfall events across two sub-periods: 1981/1982–2001/2002 and 2002/2003–2022/2023. The methodology employs four upper quantiles (Q95, Q99, Q99.5, Q99.9) to define exceptional precipitation thresholds for 1,012 grid points across mainland Portugal. An innovative severity heat map was developed to visualise changes in the mean annual number of occurrences and accumulated precipitation above these thresholds. Results reveal significant increases in the severity of exceptional precipitation across much of Portugal, particularly in urbanised and topographically complex regions. The study identifies areas where rainfall events are becoming less frequent but more intense, consistent with climate change projections. These findings have important implications for urban water management, flood risk, and infrastructure planning. The research stresses the need for adaptive water resource management strategies and improved urban resilience in the face of changing precipitation patterns. It provides empirical evidence supporting previous climate projections and highlights the importance of local characteristics in developing effective mitigation and adaptation strategies for extreme weather events in Portugal.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1716-cd

Year: 2025