Signatures of the NAO in the atmospheric circulation during wet winter months over the Mediterranean region

Positive trend of the North Atlantic Oscillation (NAO) during last several decades was also accompanied by a positive trend of the East Atlantic Western Russia (EAWR) pattern. Decline of the Mediterranean precipitation during the period has also been noted. The precipitation decline over the western part of the region has been linked to the positive trend of the NAO. Explanation for the precipitation decline over the eastern Mediterranean by the role of the EAWR trend has also been suggested. An evaluation of the hypothesis is performed in the current study. A methodology for the determination of the characterizing typical low troposphere circulation during wet-months large-scale correlation-circulation patterns is suggested. The large-scale circulation patterns for three target areas over the northwestern, north-eastern, and southeastern Mediterranean regions are constructed separately for the low and high phase periods of the teleconnection regimes. According to the results, the precipitation decline over the Mediterranean region during the last several decades of the past century is explained by the positive trend of the EAWR, which in its turn was induced by that of the NAO. The trends have lead to the changes in the typical for the wet periods of the year low-troposphere circulation regimes associated with a decline in the water vapor transport from Atlantic.