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Title
  • en Oceanic Rossby Waves over Eastern Tropical Pacific of Both Hemispheres Forced by Anomalous Surface Winds after Mature Phase of ENSO
Creator
Accessrights open access
Rights
  • en © Copyright 2016-11-10 AMS
Subject
  • Other en Intertropical convergence zone
  • Other en Sea/ocean surface
  • Other en Atmosphere-ocean interaction
  • Other en Ekman pumping/transport
  • Other en ENSO
  • Other en Rossby waves
  • NDC 452
Description
  • Abstract en 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.
Publisher en American Meteorological Society
Date
    Issued2016-11-10
Language
  • eng
Resource Type journal article
Version Type VoR
Identifier HDL http://hdl.handle.net/2115/65231
Relation
  • isIdenticalTo DOI https://doi.org/10.1175/JPO-D-15-0118.1
Journal
    • PISSN 0022-3670
      • en Journal of Physical Oceanography
      • Volume Number46 Issue Number11 Page Start3397 Page End3414
File
Oaidate 2023-07-26