Separate the Role of Southern and Northern Extra-Tropical Pacific in Tropical Pacific Climate Variability

Observational and modeling studies have elucidated the influential role played by the southern and northern extratropical Pacific (SEP and NEP) forcing in shaping dynamics of tropical Pacific climate variability. However, the relative importance of the NEP and SEP and the timescale on which they impact the tropics remain unclear. Using a linear inverse model (LIM) that selectively incorporates or excludes tropical-extratropical coupling, we find a reduction in tropical interannual variability (∼40%) and low-frequency (sub-decadal to decadal) variability in the southeastern tropical Pacific region (∼70%) in the absence of SEP. Conversely, the absence of NEP yields no significant impact on tropical interannual variability but markedly diminishes low-frequency variability in the central tropical Pacific region (∼70%). LIM and statistic diagnostics on CMIP6 models show the low-frequency to total variability ratio in the tropical Pacific depending on their NEP and SEP representation. Models with more (less) low-frequency power tend to show stronger NEP (SEP) dynamics.