How Cyclone Dynamics Shape Hydroclimate Trends in the Mediterranean

Mediterranean cyclones (MCs) are major drivers of the Mediterranean hydrological cycle (MHC), contributing up to ~70 % of regional precipitation and a substantial fraction of evaporation. Their role in regional water and energy budgets is disproportionately large relative to their spatiotemporal frequency. Despite this importance, the diversity of cyclogenesis mechanisms and their contrasting influences on key components of the hydrological and oceanic systems remain poorly understood, limiting our ability to interpret past variability and anticipate future changes in a warming climate.

In this study, we leverage a process-based classification of Mediterranean cyclones applied to 1-hourly ERA5 reanalysis tracks (1979–2020) to systematically quantify the contribution of different cyclone types to the hydrological cycle and to Mediterranean Sea heat content. The classification separates cyclones by their dominant dynamical drivers — including double-jet, daughter cyclones, thermal lows, and other mechanisms — and enables the decomposition of their individual precipitation (P) and surface evaporation (E) contributions along each cyclone track.

Our results reveal that while MCs produce a net positive annual P − E contribution over the Mediterranean, this residual has declined over recent decades. Importantly, distinct cyclone drivers exert opposing effects on hydrological and heat budgets: precipitation associated with dynamic-driven cyclones (e.g., double-jet systems) has decreased, whereas thermally driven cyclones (e.g., heat lows) have become more frequent and have enhanced evaporation. These divergent trends shift the basin-scale balance toward greater evaporative influence, with implications for regional moisture recycling and drought risk.

We further examine how the different cyclone drivers affect the ocean heat content — a key component of Mediterranean climate feedbacks — demonstrating that while most cyclones act to cool the surface by drawing heat from the ocean, some cyclone types tend to add heat to the upper ocean, generating substantial variability in the direction and magnitude of cyclone-induced air–sea exchanges.

By linking cyclone dynamics, hydrological impacts, and ocean heat content responses in a unified framework, this study advances the understanding of how different cyclogenetic processes modulate regional water and energy cycles. It underscores the importance of explicitly accounting for cyclone diversity when diagnosing Mediterranean hydroclimate variability and projecting future changes — a critical step toward improving risk assessments and adaptation strategies in this climate-sensitive region.