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Analysis of the monthly zonal index values and long‐term changes of circulation over the North Atlantic and Europe
Author(s) -
Makrogiannis T. J.,
Sahsamanoglou H. S.,
Flocas A. A.,
Bloutsos A. A.
Publication year - 1991
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.3370110503
Subject(s) - climatology , zonal and meridional , north atlantic oscillation , environmental science , index (typography) , spectral analysis , geography , atmospheric sciences , geology , physics , world wide web , computer science , quantum mechanics , spectroscopy
Mean monthly zonal index ( ZI m ) values over the North Atlantic and Europe, during the period 1873–1988, are studied. The frequency distribution of the percentage occurrence of the mean monthly ZI m values and the length of the spells of low and high ZI m values show that the predominant flow over the North Atlantic is westerly, while over Europe it is meridional. Harmonic analysis is applied to the mean annual course of the ZI m values for each of the above areas, which shows that the two first components are enough to explain more than 90 per cent of the total variance. Power spectrum analysis of the mean monthly ZI m values shows significant periodicities common to both the examined areas of the order of 18 months and less. Coherence analysis also shows that both areas are better correlated in the low frequency ranges.