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CR 21:59-81 (2002)  -  doi:10.3354/cr021059

Persistence and periodicity in the precipitation series of Turkey and associations with 500 hPa geopotential heights

M. Türkes*, U. M. Sümer, G. Kiliç

State Meteorological Service, Department of Research, PO Box 401, Ankara, Turkey

ABSTRACT: Persistence and periodicity in normalised precipitation anomaly series of 91 stations over Turkey were analysed using serial correlation coefficients and power spectra. There were considerable geographical variations and inter-seasonal contrasts with respect to periodicity and persistence characteristics. Lag-one serial correlation (L-1SC) coefficients for winter series were mostly positive and were significant at the 0.05 level for 31 stations. Annual variations at 17 stations also showed significant positive L-1SC coefficients. In contrast, year-to-year variations in spring series were characterised by negative L-1SC coefficients at most stations (significant at 18). Summer series were characterised by both positive and negative coefficients. Autumn series of most stations were random with regard to serial dependence. For winter series, long cycles of 8.4, 12-12.7, 14, 18 and 21 yr were dominant in the Marmara Transition and the Mediterranean regions, whereas short cycles of 2, 2.1, 3 and 3.2 yr were found for the Black Sea region. Major spectral peaks of most spring series occurred within spectral bands with cycles of around 2, 3, 4 and 5 yr; a 2 yr periodicity was obtained for many stations. Statistically significant negative relationships between precipitation anomalies and 500 hPa geopotential height anomalies in winter and autumn showed an apparent spatial coherence over most of Turkey. Prominent spectral peaks corresponding to about 2 and 3 yr cycles in spring precipitation anomaly series appeared to be associated with similar oscillations in spring geopotential height anomalies. A cycle of 14 yr was found for winter precipitation and geopotential height anomalies.

KEY WORDS: Turkey · Precipitation · 500 hPa geopotential height · Persistence · Power spectrum · ŒWhite¹ and Œred¹ noise continuum · Periodicity

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