Power law correlations in the Southern Oscillation Index fluctuations characterizing El Nino

摘要

The southern oscillation index (SOI) is a characteristic of the El Ninophenomenon. SOI monthly averaged data is analyzed for the time interval1866-2000. The tail of the cumulative distribution of the fluctuations of SOIsignal is studied in order to characterize the amplitude scaling of thefluctuations and the occurrence of extreme events. Large fluctuations are morelikely to occur than the Gaussian distribution would predict. The time scalingof fluctuations is studied by applying the energy spectrum and the DetrendedFluctuation Analysis (DFA) statistical method. Self-affine properties are foundto be pertinent to the SOI signal and therefore suggest power law correlationsof fluctuations of the signal. Antipersistent type of correlations exist for atime interval ranging from about 4 months to about 6 years. This leads to favorspecific physical models for El Nino description.