Wavelet Transform analysis of the length of the day and the El Niño/Southern Oscillation variations at intraseasonal and interannual time scales.
Abstract
Over the last decade, much progress has been made concerning the determination of the variations of the Earth Rotation Parameters and their physical origins. More recently, effects due to the atmospheric-oceanic El Niño-Southern Oscillation (ENSO) phenomena and to the Quasi-Biennal Oscillation have been detected in the length of day (LOD) on an interannual time-scale. In the present analysis, an approach based on the recent concept of the Wavelet Transform is used. This method gives a time-scale decomposition of the signal into localized contributions. It has been applied to parallel studies of LOD and the Southern Oscillation Index (SOI) over the interval 1962 - 1991.7 in order to explore the relationships between these series on interannual and intraseasonal time scales. The results show significant similar features between both series at low frequency, suggesting in particular the possible occurrence of a new El Niño event for 1990. For the SOI, the low-frequency oscillations seem triggered by high-frequency signals. This is not the case for LOD series, for which no relationship appears between large and small scales.
- Publication:
-
Annales Geophysicae
- Pub Date:
- June 1992
- Bibcode:
- 1992AnGeo..10..429G
- Keywords:
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- Annual Variations;
- Earth Rotation;
- El Nino;
- Southern Oscillation;
- Time Series Analysis;
- Transformations (Mathematics)