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Oceanic Rossby waves induced by the meridional shift of the ITCZ in association with ENSO events

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Title: Oceanic Rossby waves induced by the meridional shift of the ITCZ in association with ENSO events
Authors: Abe, Hiroto Browse this author →KAKEN DB
Tanimoto, Youichi Browse this author →KAKEN DB
Hasegawa, Takuya Browse this author →KAKEN DB
Ebuchi, Naoto Browse this author →KAKEN DB
Hanawa, Kimio Browse this author →KAKEN DB
Keywords: ITCZ
Meridional migration
Wind stress curl
Rossby wave
Issue Date: Apr-2014
Publisher: Springer
Journal Title: Journal of Oceanography
Volume: 70
Issue: 2
Start Page: 165
End Page: 174
Publisher DOI: 10.1007/s10872-014-0220-1
Abstract: This study investigated the eastern Pacific Intertropical Convergence Zone (ITCZ) as an atmospheric forcing to the ocean by using various observed and reanalysis data sets over 29 years. Climatologically, a zonal band of positive wind stress curl (WSC) with a 10° meridional width was exhibited along the ITCZ. A southward shift of the positive WSC band during the El Niño phase induced a negative (positive) WSC anomaly along the northern (southern) portion of the ITCZ, and vice versa during the La Niña phase. This meridional dipole accounted for more than 25 % of interannual variances of the WSC anomalies (WSCAs), based on analysis of the period 1993–2008. The negative (positive) WSCA in the northern portion of the ITCZ during the El Niño (La Niña) phase was collocated with a positive (negative) sea surface height anomaly (SSHA) that propagated westward as a Rossby wave all the way to the western North Pacific. This finding indicates that this off-equatorial Rossby wave is induced by the WSCA around the ITCZ. Our analysis of a 1.5-layer reduced gravity model revealed that the Rossby waves are mostly explained by wind stress forcing, rather than by reflection of an equatorial Kelvin wave on the eastern coastal boundary. The off-equatorial Rossby wave had the same SSHA polarity as the equatorial Kelvin wave, and generation of a phase-preserving Rossby wave without the Kelvin wave reflection was explained by meridional movement of the ITCZ. Thus, the ITCZ acts as an atmospheric bridge that connects the equatorial and off-equatorial oceanic waves.
Rights: The final publication is available at
Type: article (author version)
Appears in Collections:低温科学研究所 (Institute of Low Temperature Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 阿部 泰人

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