A Tropical–Extratropical Connection Between the Intertropical Convergence Zone and Mediterranean Hydroclimate Variability

Abstract The Mediterranean climate emerges from complex interactions between tropical and extratropical systems, yet the extent to which tropical variability, particularly that of the Intertropical Convergence Zone (ITCZ), links to Mediterranean hydroclimate remains poorly understood. Here, we show that interannual variability in ITCZ latitude, expansion, and intensity strongly and heterogeneously links with autumn (SON) precipitation across the Mediterranean Basin, revealing a previously underappreciated coupling between the tropics and extratropics. Using ERA5 reanalysis (1940–2024), we find that northward or expanded ITCZ states are linked to enhanced rainfall in the western ( ~ + 20 mm/season) and eastern ( ~ + 50 mm/season) Mediterranean. In contrast, an intensified ITCZ, marked by stronger deep convection in the tropics, is linked to suppressed rainfall in these regions (~ -20 to -50 mm/season) but increased rainfall over southern central Europe ( ~ + 100 mm/season). By ranking years by each ITCZ attribute and compositing the top and bottom 20% of seasons, we isolate the distinct atmospheric circulation patterns associated with each ITCZ variability mode. The results indicate coherent responses in integrated water-vapor fluxes, cyclone track density, and Hadley-cell overturning, which together shape regional precipitation anomalies. Enhanced moisture transport accompanies northward ITCZ displacements in the west, while increased cyclone activity drives wetter conditions in the east. Conversely, high-intensity ITCZ phases coincide with reduced cyclone density and drying over the central Mediterranean. Notably, mid-tropospheric zonal circulation shows no significant variation except in small regions of the eastern Mediterranean, suggesting that tropical links to Mediterranean rainfall may operate primarily through meridional adjustments rather than zonal shifts. Stream-function diagnostics further reveal significant differences confined to the western Mediterranean, where northward ITCZ displacements strengthen vertical ascent between ~ 25° and 35° N, linking tropical convection to mid-latitude precipitation. Together, these results suggest that ITCZ variability is a potentially important yet underexplored correlate of Mediterranean hydroclimate variability, highlighting tropical–extratropical connections that warrant further investigation for their relevance to seasonal prediction and climate projections.