Diversity of Pacific Meridional Mode and its distinct impacts on El
Niño-Southern Oscillation
Abstract
Numerous studies have demonstrated that the Pacific Meridional Mode
(PMM) plays a vital role in determining El Niño-Southern Oscillation
(ENSO) events in the following winter season. However, little attention
has been given to significant differences among the spatial patterns of
the PMM. Here we show that the PMM exhibits a large diversity in spatial
patterns, leading to distinct impacts on ENSO. Based on objective
clustering analysis, two distinct spatial patterns of the PMM are
detected. Cluster 1 (C1) PMM exhibits a strong sea surface temperature
dipole over the subtropical eastern Pacific and mid-latitude central
Pacific whereas cluster 2 (C2) features a classic dipole over the
subtropical eastern Pacific and equatorial cold tongue regions. We find
that the C1 PMM is strongly linked to ENSO events while the C2 PMM has
no statistically significant relations with following ENSO. This gives
new implications for ENSO dynamics and predictions.