Eastern pacific ITCZ dipole and ENSO diversity

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

研究成果: ジャーナルへの寄稿学術誌査読

56 被引用数 (Scopus)

抄録

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.

本文言語英語
ページ(範囲)4449-4462
ページ数14
ジャーナルJournal of Climate
31
11
DOI
出版ステータス出版済み - 6月 1 2018
外部発表はい

!!!All Science Journal Classification (ASJC) codes

  • 大気科学

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