Links Between Intraseasonal and ENSO Timescales: Insights via Geodetic and Atmospheric Analysis

We use a combination of atmospheric, oceanic and geodetic data to investigate links between intraseasonal and interannual variability in the coupled atmosphere-ocean-solid Earth system. On intraseasonal (60-100 day) time scales, strong coherence is found for length-of-day (LOD), atmospheric angular momentum (AAM), and their residual (representative of oceanic angular momentum and / or unmodeled/underrepresented atmospheric variability) with zonal wind stress in the west Pacific. Previous studies have identified wind stress in this band with the generation of basin-wide oceanic Kelvin waves, which may subsequently influence the development of sea-surface temperature (SST) anomalies in the Nino3 (eastern equatorial Pacific) region. Amplitude envelopes of LOD and AAM filtered in this band are found to be significantly correlated with monthly anomalies of Nino3 SST at a lead of 8 months, establishing a link between global indices of intraseasonal variability and the development of the ENSO cycle. The LOD-AAM residual correlates with Nino3 SST at a lead of 5 months, with the 3-month difference representing a spin-up time for atmosphere-ocean transfer of angular momentum in the west Pacific.