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Ann. Geophys., 25, 1519-1530, 2007
www.ann-geophys.net/25/1519/2007/
© European Geosciences Union 2007
Significant changes in subseries means and variances in an 8000-year precipitation reconstruction from tree rings in the southwestern USA
Jianmin Jiang1,2,3, Xiangqian Gu4, and Jianhua Ju1
1Training Center of China Meteorological Administration, Beijing, 100081, China
2Joint Institute of Marine and Atmospheric Research (JIMAR), University of Hawaii, Honolulu, HI, 96822, USA
3Pacific Fisheries Environmental Laboratory, NOAA/NMFS, Pacific Grove, CA, 93950, USA
4Chinese Academy of Meteorological Sciences, Beijing, 100081, China
Abstract. Both algorithms were applied to an 8000-year long time
series of annual precipitation that was reconstructed from tree rings in the
southwestern USA. One of the algorithms is the scanning t-test, which detects
significant changes in subseries means (the first center moments) on various
time scales. Another is the scanning F-test, which detects significant
changes in subseries variances (the second center moments) on multi-time
scales. Firstly, the scanning t-test identified 22 change points in subseries
means and partitioned the series into 23 relatively wet, normal or dry
episodes. Secondly, the scanning F-test detected 15 change points in
subseries variances and divided 16 phases in comparatively steady (with
smaller variance) or unsteady (with larger variance) features. Thirdly, the
23 wetness-episodes were characterized as the steady or unsteady situations
by jointing the results from the scanning F-test into those from the
t-test. Fourthly, the 23 episodes were compared to those in the TIC and
δ18O records from cored sediments in the deep basin of the Pyramid
Lake in Nevada by using a coherency analysis of the t-test between the
precipitation reconstruction and the TIC or δ18O series.
Fifthly, the 23 episodes were collaborated with some published papers in
related studies. In addition, the 23 episodes were also compared with
studies of the global climate change and with documents of climate changes
in China during the same periods.
As the TIC and δ18O record series are high resolution with
unequal sampling intervals between
3 and 14 years, an algorithm in the scanning t-test for dealing with the
unequal time intervals was developed in this study.
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