Distinguishing modulated oscillations from coloured noise in multivariate datasets
Climate Dynamics 12:11 (1996) 775-784
Abstract:
Extended empirical orthogonal functions (EEOFs), alternatively known as multi-channel singular systems (or singular spectrum) analysis (MSSA), provide a natural method of extracting oscillatory modes of variability from multivariate data. The eigen-functions of some simple non-oscillatory noise processes are, however, also solutions to the wave equation, so the occurrence of stable, wave-like patterns in EEOF/MSSA is not sufficient grounds for concluding that data exhibits oscillations. We present a generalisation of the "Monte Carlo SSA" algorithm which allows an objective test for the presence of oscillations at low signal-to-noise ratios in multivariate data. The test is similar to those used in standard regression, examining directions in state-space to determine whether they contain more variance than would be expected if the noise null-hypothesis were valid. We demonstrate the application of the test to the analysis of interannual variability in tropical Pacific sea-surface temperatures.CONTROL OF TROPICAL INSTABILITY WAVES IN THE PACIFIC
GEOPHYSICAL RESEARCH LETTERS 22:19 (1995) 2581-2584
Investigating the origins and significance of low‐frequency modes of climate variability
Geophysical Research Letters 21:10 (1994) 883-886
Abstract:
An analysis of the 130‐year record of the Earth's global mean temperature reveals a significant warming trend and a residual consistent with an auto‐correlated (“red”) noise process whose predictability decays with a timescale of two years. Thus global temperatures, in isolation, do not indicate oscillations at 95% confidence against a red noise null hypothesis. Weak signals identified in the global series can, however, be traced to significant sea surface temperature oscillations in the equatorial Atlantic (period ∼10 years) and the El Niño region of the Pacific (3–5 years). No robust evidence is found in this data for interdecadal oscillations, The 10‐year Atlantic oscillation corresponds to a pattern of temperature anomalies which has been associated with interannual variations in West African rainfall and in U.S. hurricane landfall frequency. Copyright 1994 by the American Geophysical Union.CLIMATE SENSITIVITY AND TROPICAL MOISTURE DISTRIBUTION
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 99:D2 (1994) 3707-3716