The relevance of the North-Sea Caspian Pattern (NCP) in explaining temperature variability in Europe and the Mediterranean

Abstract

Abstract. The impact of the upper level (500 hPa) teleconnection between the North-Sea and the Caspian (NCP) on the temperature and precipitation regimes in the Eastern Mediterranean (EM) have been studied and reported and an index (NCPI) that measures the normalized geopotential heights' differences between the two poles of this teleconnection has been defined. In the present study, the impact of the NCP on the temperature regime over the entire European continent is presented. In particular, the correlation between temperature and the NCPI has been evaluated, on a monthly basis, over the entire Euro-Mediterranean domain for the 1948–2007 period. The results highlight a significant positive correlation in the north-western area of the domain and a significant negative correlation in the south-eastern one. These two poles were also highlighted by comparing the temperature anomalies associated with both phases of NCP. The importance of this sort of NCP-induced temperature bi-pole in the context of temperature variability over Europe and the Mediterranean has been evaluated by applying a Principal Component Analysis to the temperature dataset. The results showed that the temperature bi-pole is associated with the second most important mode of temperature variability over the domain, but if the analysis is restricted to the months associated to NCP (+) and NCP (−), it becomes the first mode with 29.2 % of associated variance.