The workshop will focus on impacts in the Mediterranean basin of the North Atlantic Oscillation (NAO). This will constitute a unique forum to present the state of the art of the numerous studies undertaken on Hydrological, Socioeconomic and Ecological impact of the NAO. As such it aims to gather the expertise of researchers from several complementary earth science fields (Geography, Hydrology, Remote-sensing, Climatology, Agriculture, Energy), but that have been lacking a common ground.

Previous work has shown that the interannual variability of Mediterranean climate is mostly associated to changes in certain relevant atmospheric circulation patterns. Such changes can have significant impacts in the climate of this region but also on the natural environment and several socioeconomic activities. Among these patterns, the North Atlantic Oscillation (NAO) is the only one which shows a clear signal throughout the whole year, but with stronger intensity and extension during winter due to the stronger meridional gradients. During this season changes in the NAO phase lead to shifts in the location of the centers of action and in the associated storm tracks.

The NAO is responsible for most of the climatic variability in the North Atlantic, modifying direction and intensity of the westerlies, the track of the polar depressions and the location of the anticyclones. During the positive phases, the Azores subtropical high is reinforced, leading to a driest weather in the Mediterranean region. On the contrary, during the negative winters, cyclones move southward increasing precipitation on the western Mediterranean.

The NAO behavior is characterized by a remarkable interannual variability, which is evident in paleo and instrumental records. In the instrumental period, the NAO has shown a decreasing trend between 1940 and 1970. But the last decades of the 20th century have shown a higher persistence of positive phases, coincident with severe drought conditions in the Mediterranean, and with stronger variability. The increase in frequency and strength in the positive phases seems to be unprecedented in the instrumental record.

The complexity of the NAO behavior and their impact has attracted the attention of a wide variety of scientific communities, with more than 2800 papers published on different NAO features during the last decade. The association between the NAO and the Mediterranean climate variability has been well documented, showing that it as one of the main forcings in the region. Its impact on extreme events such as droughts, severe precipitations or heat and cold waves has been well established. These changes have also an impact on the availability of water resources of the whole basin, affecting, not only river flows but also storage availability in lakes and reservoirs and snow cover. The ecological dynamics of the region is also greatly affected, as has been shown through satellite imagery and tree rings. This has an impact on the quality and quantity of crops and in the migration and welfare of animal populations. The marine environment is also affected by NAO through changes in sea level and fisheries dynamics. Other reported impacts are landslides, air pollution and human health.