North Sea-Caspian pattern (NCP) - An upper level atmospheric teleconnection affecting the Eastern Mediterranean: Identification and definition

An upper level atmospheric teleconnection between grid points: 0°, 55° N; 10° E, 55° N (North Sea) and 50° E, 45° N; 60° E, 45° N (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. Except for September, no significant temporal trends were found. Negative and positive phases of the NCP (NCP(-) and NCP(+), respectively) were defined using standardized scores. A classification of all months into NCP(-), NCP(+) or normal conditions during the analysis period (1958-1998) was prepared and analysed. No significant correlation was found between the NCPI and the NAO index. The anomalous circulation during either NCP(-) or NCP(+) conditions is defined and its possible impact on the regional climate is discussed. Preliminary results show below normal temperatures and above normal precipitation in the Balkans and the Middle East during NCP(+), and the opposite for NCP(-).