A decadal tropical Pacific condition unfavorable to central Pacific El Niño

• Published in: Geophysical research letters Vol. 44; no. 15; pp. 7919 - 7926
• Main Authors: Zhong, Wenxiu, Zheng, Xiao‐Tong, Cai, Wenju
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.08.2017
• Subjects: Advection; Central Pacific El Niño; Computational fluid dynamics; decadal background; Earth; El Nino; El Nino events; El Nino phenomena; ENSO frequency; Feedback; Fluid dynamics; Geophysics; Hydrodynamics; Integration; Modes; Ocean currents; Ocean temperature; Sea surface; Sea surface temperature; Surface temperature; Temperature (air-sea); Trade winds; Tropical climate; tropical variability; Variability; zonal advection
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2017GL073846

The frequency of central Pacific (CP) El Niño 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 Niño 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 Niño developing season, resulting in the low CP El Niño frequency. Key Points Central Pacific El Nino frequency is affected by decadal states jointly contributed by two major tropical Pacific decadal variability A positive phase of tropical Pacific decadal variability with a negative Interdecadal Pacific Oscillation is unconducive to the frequency Under such a decadal state, anomalous eastward currents occur infrequently, suppressing positive zonal advection feedback