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Nonlinear Zonal Wind Response to ENSO in the CMIP5 Models: Roles of the Zonal and Meridional Shift of the ITCZ/SPCZ and the Simulated Climatological Precipitation

Author(s): Choi, Kit-Yan; Vecchi, Gabriel A; Wittenberg, Andrew T

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Abstract: The observed equatorial Pacific zonal wind response during El Niño tends to be stronger than during La Niña. Most global coupled climate models in phase 5 of CMIP (CMIP5) exhibit such nonlinearity, although weaker than observed. The wind response nonlinearity can be reproduced by driving a linear shallow water atmospheric model with a model’s or the observed precipitation anomalies, which can be decomposed into two main components: the zonal and meridional redistribution of the climatological precipitation. Both redistributions contribute comparably to the total rainfall anomalies, whereas the zonal redistribution plays the dominant role in the zonal wind response. The meridional redistribution component plays an indirect role in the nonlinear wind response by limiting the zonal redistribution during La Niña and thus enhancing the nonlinearity in the wind response significantly. During La Niña, the poleward movement of the ITCZ/SPCZ reduces the equatorial zonal-mean precipitation available for the zonal redistribution and its resulting zonal wind response. Conversely, during El Niño, the equatorward movement of the ITCZ and SPCZ do not limit the zonal redistribution of precipitation. The linear equatorial zonal wind response to ENSO is found to have a significant linear correlation with the equatorial central Pacific climatological precipitation and SST among the CMIP5 models. However, no linear correlation is found between the nonlinear equatorial zonal wind response and the climatological precipitation.
Publication Date: 1-Nov-2015
Citation: Choi, Kit-Yan, Gabriel A. Vecchi, and Andrew T. Wittenberg. "Nonlinear zonal wind response to ENSO in the CMIP5 models: Roles of the zonal and meridional shift of the ITCZ/SPCZ and the simulated climatological precipitation." Journal of Climate 28, no. 21 (2015): 8556-8573. doi:10.1175/JCLI-D-15-0211.1.
DOI: doi:10.1175/JCLI-D-15-0211.1
ISSN: 0894-8755
EISSN: 1520-0442
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Pages: 8556 - 8573
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Climate
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.
Notes: Related Item links to supplemental information.

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