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Evidence of an 11‐year periodicity in tree‐ring series from formosa related to the sunspot cycle
Author(s) -
Mori Yukihiro
Publication year - 1981
Publication title -
journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0196-1748
DOI - 10.1002/joc.3370010407
Subject(s) - series (stratigraphy) , sunspot , sunspot number , dendrochronology , tree (set theory) , ring (chemistry) , physics , mathematics , solar cycle , astrophysics , geography , combinatorics , geology , chemistry , paleontology , archaeology , organic chemistry , quantum mechanics , magnetic field , solar wind
Abstract It has been pointed out previously that tree‐ring series from Formosa show an 11‐year periodicity related to the sunspot cycle. However, significance tests of this finding have not been made and therefore the statistical reliability has not been known. Spectra of tree‐ring series from other sites reported before show no evidence that the 11‐year sunspot cycle appears in tree‐ring series. Spectral analyses have been made of published tree‐ring data from Formosa and previous studies have been re‐examined. Tree‐ring series from two different sites in Formosa show an 11‐year spectral peak at the level of confidence higher than 90%. Cross spectral analysis between the tree‐ring series and the Zurich annual sunspot number shows that the 11‐year fluctuations in the tree‐ring series are related to the sunspot cycle with a time lag of 1/4 phase at the 99% confidence level. Using a band‐pass filter technique, it is found that the 11‐year fluctuations in tree‐ring series correspond to almost each cycle of the sunspot number except for periods of low solar activity. Significant 11 ‐year fluctuations in the tree‐ring series appear during most of the periods of an ‘active’ sun as estimated by carbon 14 abundance in tree‐rings.