Eastern pacific ITCZ dipole and ENSO diversity

Shang Ping Xie, Qihua Peng, Youichi Kamae, Xiao Tong Zheng, Hiroki Tokinaga, Dongxiao Wang

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The eastern tropical Pacific features strong climatic asymmetry across the equator, with the intertropical convergence zone (ITCZ) displaced north of the equator most of time. In February-April (FMA), the seasonal warming in the Southern Hemisphere and cooling in the Northern Hemisphere weaken the climatic asymmetry, and a double ITCZ appears with a zonal rainband on either side of the equator. Results from an analysis of precipitation variability reveal that the relative strength between the northern and southern ITCZ varies from one year to another and this meridional seesaw results from ocean-atmosphere coupling. Surprisingly this meridional seesaw is triggered by an El Niño-Southern Oscillation (ENSO) of moderate amplitudes. Although ENSO is originally symmetric about the equator, the asymmetry in the mean climate in the preceding season introduces asymmetric perturbations, which are then preferentially amplified by coupled ocean-atmosphere feedback in FMA when deep convection is sensitive to small changes in cross-equatorial gradient of sea surface temperature. This study shows that moderate ENSO follows a distinct decay trajectory in FMA and southeasterly cross-equatorial wind anomalies cause moderate El Niño to dissipate rapidly as southeasterly cross-equatorial wind anomalies intensify ocean upwelling south of the equator. In contrast, extreme El Niño remains strong through FMA as enhanced deep convection causes westerly wind anomalies to intrude and suppress ocean upwelling in the eastern equatorial Pacific.

Original languageEnglish
Pages (from-to)4449-4462
Number of pages14
JournalJournal of Climate
Volume31
Issue number11
DOIs
Publication statusPublished - Jun 1 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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    Xie, S. P., Peng, Q., Kamae, Y., Zheng, X. T., Tokinaga, H., & Wang, D. (2018). Eastern pacific ITCZ dipole and ENSO diversity. Journal of Climate, 31(11), 4449-4462. https://doi.org/10.1175/JCLI-D-17-0905.1