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Excitation of the Earth's Chandler wobble by southern oscillation/El Nino, 1900-1979The southern oscillation/El Nino (ENSO) is the single most prominent interannual signal in global atmospheric/oceanic fluctuations. The following question is addressed: how important is the angular momentum carried by ENSO in exciting the Earth's Chandler wobble? The question is attacked through a statistical analysis of the coherence spectra (correlation as a function of frequency) between two data sets spanning 1900 to 1979-the southern oscillation index (SOI) time series and the excitation function psi (with x-component psi sub x and y-component psi sub y) of the Chandler wobble derived from the homogeneous ILS (International Latitude Service) polar motion data. The coherence power and phase in the Chandler frequency band (approx. 0.79 to 0.89 cpy) are studied. It is found that, during 1900 to 1979 the coherence between SOI and psi sub x is significant well over the 95% confidence threshold whereas that between SOI and psi sub y is practically nil. Quantitatively, the coherence study shows that ENSO provides some 20% of the observed Chandler wobble excitation power. Since earlier investigations have shown that the total atmospheric/oceanic variation can account for the Chandler wobble excitation at about 20% level, the implication is that ENSO maybe an important (interannual) part of the atmospheric/oceanic variation that is responsible for the Chandler wobble excitation during 1900 to 1979.
Document ID
19860010242
Document Type
Technical Memorandum (TM)
Authors
Chao, B. F. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
September 5, 2013
Publication Date
September 1, 1985
Subject Category
EARTH RESOURCES AND REMOTE SENSING
Report/Patent Number
REPT-85B0557
NASA-TM-86231
NAS 1.15:86231
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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