Atlantic and Mediterranean influence promoting an abrupt change in winter precipitation over the southern Iberian Peninsula

Abstract

The Mediterranean basin was identified decades ago as a potential hotspot region under global warming, where droughts and floods keep increasing. However, uncertainties about how the water cycle is being affected by the climate change still remain. Henceforth, this study analyses the recent variability of winter precipitation (WP) in Andalusia, the southern Iberian Peninsula (IP), and their relationship with the Atlantic and Mediterranean sources. For that purpose, two representative teleconnection patterns were used: the NAO (Atlantic influence) and WeMO (Mediterranean) indexes. The results of this contribution revealed that WP mostly decreased in the target region, only increasing over south-eastern Andalusia. Also, the influence area of WeMO increased and its modulation magnitude in WP behaviour. In addition, series of these atmospheric patterns presented a breakpoint since 1980s towards NAO+ and WeMO-. Therefore, this contribution concludes that Andalusia can be divided into three areas based on the WP behaviour: (1) NAO-correlated (WeMO uncorrelated) where WP decreased; (2) NAO and WeMO-correlated, where WP did not change; and (3) WeMO correlated (NAO uncorrelated) where WP increased. Likewise, the extent of those regions mostly is determinate by geographical features. The orography does not allow the enhancement of the WeMO influence across large areas of Andalusia. As a result, WeMO- cannot compensate reductions of WP caused by NAO+, which concentrates WP reductions on its windward (most areas of Betic Mountains, where WeMO uncorrelated). Meanwhile, WeMO- promote WP increases on its windward in the Betic Mountains (eastern slopes, south-eastern Andalusia); and coastal areas/Guadalquivir Valley where Mediterranean influence does not find a barrier effect caused by the relief.