Interannual variations in length of day with respect to El Niño - Southern Oscillation’s impact (1962–2015)

The objective of research done in this study is to examine the variability of the length of day (LOD) and to investigate its correlation with ENSO (El Nino-Southern oscillation) episodes. For this purpose, the LOD time series (1962–2015), from the International Earth Rotation and Reference Systems Service (IERS), is investigated using the Singular Spectrum Analysis (SSA) technique. The results show that the LOD time series is very complex and is composed of several components: the long-term trend explains 95.97% of the original series, the annual harmonic 1.76% and the semi-annual 1.35%. Considering sea surface temperature anomalies (SSTA) index over the Nino3, Nino4 and Nino3.4 regions, Southern Oscillation Index (SOI) and Multivariate ENSO Index (MEI), the residuals signal, that represents only 0.92% of the initial LOD series, indicate a significant correlation with ENSO occurred during 1965–66, 1972–73, 1982–83 and 1997–98 El Nino events and 1970–71, 1973–74, 1988–89, 2007–08, 2010–11 La Nina ones. This is a pertinent result that suggests that LOD variability is at least partly related to ENSO phenomena.