LAUSR

The frequency of central Pacific (CP) El Nino events displays strong decadal-variability but the associated dynamics are unclear. The Interdecadal Pacific Oscillation (IPO) and the Tropical Pacific Decadal Variability (TPDV) are two dominant modes of tropical Pacific decadal variability that can interact with high-frequency activities. Using a 500-year control integration from the Geophysical Fluid Dynamics Laboratory Earth System Model, we find that the difference in mean state between the low-frequency and high-frequency CP El Nino periods is similar to the decadal background condition concurrently contributed by a negative IPO and a positive TPDV. This decadal state features strengthened trade winds west of the International Date Line and anomalous cool sea surface temperatures across the central tropical Pacific. As such, positive zonal advection feedback is difficult to be generated over the central-to-western tropical Pacific during the CP El Nino developing season, resulting in the low CP El Nino frequency.