Oceanic Rossby Waves over Eastern Tropical Pacific of Both Hemispheres Forced by Anomalous Surface Winds after Mature Phase of ENSO

Abe, Hiroto; Tanimoto, Youichi; Hasegawa, Takuya; Ebuchi, Naoto

Oceanic Rossby Waves over Eastern Tropical Pacific of Both Hemispheres Forced by Anomalous Surface Winds after Mature Phase of ENSO

Abe, Hiroto; Tanimoto, Youichi; Hasegawa, Takuya et al.

Journal of Physical Oceanography, 2016, 46(11), 3397-3414

Permalink : https://hdl.handle.net/2115/65231

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アクセス権	open access
URI	https://hdl.handle.net/2115/65231
タイトル	Oceanic Rossby Waves over Eastern Tropical Pacific of Both Hemispheres Forced by Anomalous Surface Winds after Mature Phase of ENSO
著者	Abe, Hiroto ; Tanimoto, Youichi ; Hasegawa, Takuya ; Ebuchi, Naoto
e-Rad_Researcher 40627246 著者名 Abe, Hiroto
e-Rad_Researcher 00291568 著者名 Tanimoto, Youichi
著者名 Hasegawa, Takuya
e-Rad_Researcher 10203655 著者名 Ebuchi, Naoto
言語	英語
キーワード	Intertropical convergence zone
	Sea/ocean surface
	Atmosphere-ocean interaction
	Ekman pumping/transport
	ENSO
	Rossby waves
発行日	2016-11-10
出版者	American Meteorological Society
収録物名	Journal of Physical Oceanography
巻(号)	46(11)
ページ	3397-3414
抄録	The present study examined ENSO-related wind forcing contribution to off-equatorial Rossby wave formations in the eastern tropical regions of the North and South Pacific using satellite altimeter data and atmospheric reanalysis data during the period of 1993–2013. After mature phases of ENSO events, the sea surface height anomaly fields showed that off-equatorial Rossby waves propagated westward along 11°N and 8°S from the eastern Pacific. Starting longitudes of the westward propagation were distant from the eastern coast, especially for weak El Niño events in the 2000s, in contrast to the strong 1997/98 El Niño event in which the propagations started from the coast. Based on observational data, it was hypothesized that the Rossby waves could be formed by off-equatorial zonal belts of wind stress curl anomalies (WSCAs) in 135°–90°W rather than by wave emissions from the eastern coast. A numerical model forced only by WSCAs, that is, without wave emissions from the coast, successfully reproduced observed features of the Rossby waves in 180°–120°W, supporting the study’s hypothesis. During mature phases of El Niño events, equatorially symmetric negative sea level pressure anomalies (SLPAs) resulting from hydrostatic adjustment to the underlying warm sea surface temperature anomalies dominated over the eastern tropical Pacific. Anomalous surface easterlies blowing around the negative SLPA area as geostrophic winds were a major contributor in forming the anticyclonic WSCAs. The polarity of the anomalies is reversed during La Niña events. Therefore, spatial patterns of the SLPAs associated with the ENSO events are necessary to understand the Rossby wave formations.
資源タイプ	学術雑誌論文
出版タイプ	Version of Record
権利情報	© Copyright 2016-11-10 AMS
PISSN	0022-3670
関連情報 (isIdenticalTo)	出版社版DOI https://doi.org/10.1175/JPO-D-15-0118.1