Mediterranean precipitation variability is driven by complex atmospheric mechanisms beyond the North Atlantic Oscillation

Abstract Precipitation variability in the Mediterranean Basin has traditionally been attributed to large-scale Atlantic climate modes, particularly the North Atlantic Oscillation (NAO). However, over key regions such as the Italian Peninsula, NAO-based interpretations often fall short in explaining observed hydroclimatic patterns. In this study, we combine deep learning reconstruction of historical precipitation records from 1950 to 2020 with the analysis of atmospheric teleconnection indices and air mass back-trajectory modelling. Using a dataset of more than eleven thousand rain gauge time series, we developed neural network models to produce a continuous and high-resolution precipitation dataset for Italy. Our results demonstrate that Mediterranean teleconnections, especially the Mediterranean Oscillation Index (MOI) and the Western Mediterranean Oscillation (WeMO), exert a stronger and more consistent influence on precipitation compared to the NAO. Trajectory analysis using the HYSPLIT model reveals that the Western Mediterranean is the dominant moisture source for central and northern Italy, while the Ionian and Eastern Mediterranean regions become increasingly important in the southern part of the country. These findings underscore the central role of Mediterranean cyclogenesis in shaping regional precipitation dynamics and call for a reassessment of climate interpretation frameworks that have traditionally focused on Atlantic influences alone.