Recent changes in temperature extremes across the north-eastern region of Italy and their relationship with large-scale circulation

The present study is an analysis of recent changes (1981-2016) in air temperature across the north-eastern region of Italy (NERI), located in a transition zone influenced by the Mediterranean and continental climatological regimes. Annual and seasonal trends in mean maximum and minimum temperatures as well as in selected extreme indices are investigated using high-quality and homogenised daily data deriving from a distributed network of 50 weather stations. The results reveal an overall widespread warming, particularly intense in spring and summer, with significant positive trends in mean and daytime (maximum-related) temperature extremes, especially at lower altitudes. No substantial elevation dependency is observed for trends in minimum-related temperature indices, which are generally characterised by lower spatial variability. Comparable positive and negative trends are identified in the frequency and duration of warm- and cold-related extremes indices. Finally, the influence on temperature extremes of dominant large-scale circulation modes in southern Europe (North Atlantic Oscillation [NAO] and East-Atlantic [EA] pattern) is examined. The results indicate that especially NAO-induced changes can explain observed temperature trends over the NERI, while the impact of the EA pattern is slightly weaker.