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Linking the North American Dipole to the Pacific Meridional Mode

Lookup NU author(s): Dr Xiaofeng Li

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by Wiley-Blackwell Publishing, Inc., 2019.

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Abstract

The North American dipole (NAD) represents a meridional dipole of sea level pressure anomalies over the western tropical North Atlantic and northeastern North America. This study demonstrates that the NAD is intimately linked to the development of the Pacific meridional mode (PMM). In addition to the North Pacific Oscillation, the NAD provides another important remote forcing source to trigger the PMM. The NAD influences the PMM through both direct and indirect pathways. The direct effect is that the winter NAD influences the sea surface temperature (SST) and surface winds over the northeastern subtropical Pacific (NESP) through concurrent anticyclonic flow associated with the NAD, which tends to generate a weak initial warming over the NESP region during late winter and early spring. The indirect effect is that the NAD first induces SST cooling over the northern tropical Atlantic during spring, and the northern tropical Atlantic SST cooling then generates a low‐level anticyclonic flow anomaly over the NESP, which further strengthens the surface warming over the NESP, thereby causing the development of the PMM in the following months. The NAD can also exert an influence on the El Niño–Southern Oscillation through its effects on the PMM. In particular, El Niño episodes led by the combined NAD‐PMM events tend to take the form of the central Pacific El Niño, rather than the canonical eastern Pacific El Niño. We suggest that a better understanding of the NAD‐PMM‐El Niño–Southern Oscillation dynamic link could be useful for the prediction of different types of El Niño event.

Publication metadata

Author(s): Ding R, Li J, Tseng Y, Sun C, Li Y, Xing N, Li Xiao-Feng

Publication type: Article

Publication status: Published

Journal: Journal of Geophysical Research: Atmospheres

Year: 2019

Volume: 124

Issue: 6

Pages: 3020-3034

Print publication date: 27/03/2019

Online publication date: 04/03/2019

Acceptance date: 22/02/2019

Date deposited: 16/05/2019

ISSN (print): 2169-897X

ISSN (electronic): 2169-8996

Publisher: Wiley-Blackwell Publishing, Inc.

URL: https://doi.org/10.1029/2018JD029692

DOI: 10.1029/2018JD029692

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