A review on the impact of the North Sea - Caspian Pattern (NCP) on temperature and precipitation regimes in the middle east

An upper level atmospheric teleconnection between grid points: 0, 55N; 10E, 55N (North Sea) and 50E, 45N; 60E, 45N (northern Caspian) was identified. This teleconnection, referred as the North Sea-Caspian Pattern (NCP) is evident at the 500 hPa level. The NCP is more pronounced during winter and the transitional seasons. An index (NCPI) measures the geopotential heights differences between the two poles of the NCP. Time series of the NCPI are presented and analysed. A calendar of all months according to their belonging to NCP(-), NCP(+) or normal conditions during the analysis period (1958.1998) was prepared. The associated anomaly circulation during either NCP(-) or NCP(+) conditionswas defined and their impact on the regional temperature and precipitation regimes in Greece, Turkey and Israel is analysed. At all stations and in all months, temperature values were significantly higher during the NCP (-) as compared with the NCP (+). Furthermore, apart from very few exceptions, the absolute monthly mean maximum and monthly mean minimum values were obtained during the NCP (-) and the NCP (+) phases, respectively. The maximum impact of the NCP on mean air temperature was detected in the continental Anatolian Plateau, where the mean seasonal differences are above 3.5.C. This influence decreases westwards and southwards. The influence on the rainfall regime is more complex. Regions exposed to the southern maritime trajectories, in Greece and in Turkey, receive more rainfall during the NCP (-) phase, whereas in the regions exposed to the northern maritime trajectories, such as Crete in Greece, the Black Sea region in Turkey, and in all regions of Israel, there is more rainfall during the NCP (+) phase. The accumulated rainfall differences between the two phases may be over 50% of the seasonal average for some stations.