Investigating the Combined Influence of the North Atlantic Oscillation and the East Atlantic Pattern on Monthly Precipitation Across Mainland Spain

The combined influence of the NAO and EA on monthly precipitation across mainland Spain remains insufficiently understood despite their recognized importance for European climate variability. This study investigates how individual and combined NAO and EA phases influence monthly precipitation patterns across mainland Spain using the MOPREDAScentury dataset between January 1950 and December 2020. Spatial correlation analyses and precipitation deviation mapping were used to identify regional and seasonal precipitation responses associated with each teleconnection phase. The results demonstrate that combined NAO/EA phases produce distinct precipitation signatures that vary considerably throughout the year, with the strongest and most spatially coherent relationships occurring during winter. Concurrent NAO−/EA −phases were associated with significantly wetter conditions, whereas NAO+/EA− phases generally produced drier conditions across much of mainland Spain. The influence of the NAO weakened through summer, while the EA became a more important control on precipitation variability. These findings demonstrate that considering the NAO and EA together provides a more comprehensive understanding of precipitation variability than analyzing either teleconnection independently, with potential applications for seasonal forecasting, drought preparedness and water resource management.