Triple-dip La Niña in 2020–23: understanding the role of the annual cycle in tropical Pacific SST

Autor: Song Jiang, Congwen Zhu, Zeng-Zhen Hu, Ning Jiang, Fei Zheng
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: Environmental Research Letters, Vol 18, Iss 8, p 084002 (2023)
Druh dokumentu: article
ISSN: 1748-9326
DOI: 10.1088/1748-9326/ace274
Popis: The triple-dip La Niña in 2020–23 is characterized by persisting southeasterly wind anomalies over the tropical central and eastern Pacific. Our results show that the wind anomalies are associated with the anomalously negative phase of the first two leading modes of the annual cycle (antisymmetric and symmetric modes about the equator) of sea surface temperature (SST) in the tropical Pacific. The two modes account for 82.2% and 13.5% of the total variance, linking to the seasonal swing of SST between the northern and southern hemispheres and the temporal evolution of El Niño-Southern Oscillation, respectively. During 2020–23, the persistently and anomalously negative phase of the symmetric mode enhances easterly wind over the tropical central Pacific, while the antisymmetric mode strengthens the southeasterly wind over the tropical eastern Pacific. The anomalously negative phase of the antisymmetric mode is associated with the contrast of SST anomalies between the northern and southern hemispheres, which provided a favorable background for the triple-dip La Niña in 2020–23.
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