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Geophysical Monograph Series

 

Keywords

  • tree ring
  • principal component
  • temperature
  • wavelet spectra
  • Fourier spectra
  • western Himalayas

Index Terms

  • 1605 Global Change: Abrupt/rapid climate change
  • 4425 Nonlinear Geophysics: Critical phenomena
  • 1650 Global Change: Solar variability
  • 3255 Mathematical Geophysics: Spectral analysis

Article

GEOPHYSICAL MONOGRAPH SERIES, VOL. 196, PP. 169-176, 2012

Empirical Orthogonal Function Spectra of Extreme Temperature Variability Decoded From Tree Rings of the Western Himalayas

R. K. Tiwari

National Geophysical Research Institute, CSIR, Hyderabad, India


R. R. Yadav

Birbal Sahni Institute of Paleobotany, Lucknow, India


K. P. C. Kaladhar Rao

National Geophysical Research Institute, CSIR, Hyderabad, India


The ability to distinguish different natural frequency modes from a complex noisy temperature record is essential for a better understanding of the climate response to internal/external forcing. Here we investigate the empirical orthogonal function and spectra of a newly reconstructed tree ring temperature variability record decoded from the western Himalayas for a period spanning 1227 A.D. to 2000 A.D., allowing frequency resolution of interdecadal and interannual oscillatory modes. The spectral analysis of first principal component (PC1) with ∼61.46% variance reveals the dominance of significant solar cycles notably peaking around 81, 32, 22, and 8–14 years. Although longer solar cycles are dominant and statistically significant at more than 95% confidence level, the average 11 year solar cycle peaking at a period ranging from 8 to 14 years is less significant (not >90%) and might indicate chaotic phenomena. Similar spectral analysis of PC2 (variance 26%) and PC3 (variance 13.05%) reveals interannual oscillations peaking at a period range of 2–8 years, which are probably related to the global aspect of the El Niño–Southern Oscillation phenomena. Our present analysis in the light of the recent ocean-atmospheric model results suggests that even small variation in solar output in conjunction with the atmospheric-ocean system and other related feedback processes could cause the observed abrupt temperature variability at the time of “criticality” through the triggering mechanism.

Citation: Tiwari, R. K., R. R. Yadav, and K. P. C. Kaladhar Rao (2012), Empirical orthogonal function spectra of extreme temperature variability decoded from tree rings of the western Himalayas, in Extreme Events and Natural Hazards: The Complexity Perspective, Geophys. Monogr. Ser., vol. 196, edited by A. S. Sharma et al. 169–176, AGU, Washington, D. C., doi:10.1029/2011GM001133.

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