Using observations and reanalysis, we develop a robust statistical approach based on canonical correlation analysis (CCA) to explore the leading drivers of decadal and longer-term Mediterranean hydroclimate variability during the historical, half-year wet season. Accordingly, a series of CCA analyses are conducted with combined, multi-component large-scale drivers of Mediterranean precipitation and surface air temperatures. The results highlight the decadal-scale North Atlantic Oscillation (NAO) as the leading driver of hydroclimate variations across the Mediterranean basin. Markedly, the decadal variability of Atlantic-Mediterranean sea surface temperatures (SST), whose influence on the Mediterranean climate has so far been proposed as limited to the summer months, is found to enhance the NAO-induced hydroclimate response during the winter half-year season. As for the long-term, century scale trends, anthropogenic forcing, expressed in terms of the global SST warming (GW) signal, is robustly associated with basin-wide increase in surface air temperatures. Our analyses provide more detailed information than has heretofore been presented on the sub-seasonal evolution and spatial dependence of the large-scale climate variability in the Mediterranean region, separating the effects of natural variability and anthropogenic forcing, with the latter linked to a long-term drying of the region due to GW-induced local poleward shift of the subtropical dry zone. The physical understanding of these mechanisms is essential in order to improve model simulations and prediction of the decadal and longer hydroclimatic evolution in the Mediterranean area, which can help in developing adaptation strategies to mitigate the effect of climate variability and change on the vulnerable regional population.

使用观察和重新分析，我们开发了基于典范相关分析（CCA）的可靠统计方法，以探索历史性半年湿季中十年和长期地中海水文气候变化的主要驱动因素。因此，对地中海降水和地表气温的综合，多成分大规模驱动因素进行了一系列CCA分析。研究结果突显了十年尺度的北大西洋涛动（NAO）是整个地中海盆地水文气候变化的主要驱动力。值得一提的是，迄今为止，大西洋-地中海海表温度（SST）的年代际变化一直被认为仅限于夏季，其对地中海气候的影响，发现在冬季半年期间可以增强NAO诱导的水气候响应。至于长期的世纪尺度趋势，以全球海表温度增高（GW）信号表示的人为强迫与全盆地地表气温的上升密切相关。我们的分析提供了迄今为止关于地中海地区大规模气候变化的次季节演变和空间依赖性的更详细的信息，将自然变化和人为强迫的影响分开了，后者与长期以来的长期变化有关。由于GW引起的亚热带干燥区局部极地偏移，导致该区域长期干燥。