Spatial organization in Europe of decadal and interdecadal fluctuations in annual rainfall

• Published in: International Journal of Climatology
• Main Authors: Lucero, Omar A., Rodríguez, Norma C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2002
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: http://dx.doi.org/10.1002/joc.756; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.756; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.756

Abstract The spatial patterns of decadal and bidecadal fluctuations in annual rainfall in Europe are identified. Filtering of time series of the anomaly in annual rainfall is carried out using the Morlet wavelet technique. Reconstruction is achieved by summing the contributions from bands of wavelet time scales; the decadal band and the bidecadal band are composed of contributions from the bands of the (10 to 17 year) and (17 to 27 year) time scales respectively. Results indicate that (1) the spatial organization of the decadal and bidecadal components of annual rainfall are standing‐wave‐like organized patterns. Three standing decadal fluctuations zonally aligned formed the spatial pattern from 1900 until 1931; thereafter the pattern changed into a NW–SE orientation. The decadal band shows an average 12 year period. (2) The spatial organization of the bidecadal component was composed of three standing fluctuations from 1903 to 1986. After 1987, two standing bidecadal fluctuations were located over Europe. The orientation of the bidecadal fluctuations changed during the period under study. Until 1913 the spatial pattern of the bidecadal component was zonally aligned. Since 1913 and until 1986 the three bidecadal fluctuations composing the spatial pattern were aligned SW–NE; starting in 1987, the spatial pattern is composed of two standing fluctuations zonally aligned. The bidecadal spatial pattern shows an average period of 20 to 22 years in length. (3) At the decadal and bidecadal time scales, the first principal component of the spatial field of anomaly in annual rainfall and the North Atlantic oscillation (NAO) index are connected. The upper positive third (lower negative third) of values of the first principal component are indicative of an extensive area with positive (negative) anomalies in annual rainfall. (4) At the decadal time scale the relative phase between the first principal component and the NAO index changes through the period under study; these changes define three regimes. (i) During the regime ...