Abstract
The triple-dip La Niña in 2020-22 is characterized by persisting
easterly and southeasterly wind anomalies over the tropical central and
southeastern Pacific. Our results show that the wind anomalies are
associated with two leading modes of the annual cycle (antisymmetric and
symmetric modes) of sea surface temperature (SST). The first two modes account
for 82.2% and 13.5% of total variances, linking to the seasonal swing
of SST distribution in the northern and southern hemispheres and the
temporal evolution of El Niño-Southern Oscillation (ENSO), respectively. The
persistent negative phase of the symmetric mode enhances easterly wind,
while the antisymmetric mode strengthens the southeasterly wind. The
negative phase of the antisymmetric mode is regulated by the contrast of
SST anomalies between the northern and southern hemispheres. Therefore,
both the zonal and the meridional process associated with annual cycle
anomalies may play an important role in the evolution of the triple-dip
La Niña in 2020-22.