Analysis of the differences between the North Pacific Victoria and meridional modes

The Victoria mode (VM) and Pacific meridional mode (PMM) are the dominant SST modes over the North Pacific. Both are forced by a North Pacific Oscillation (NPO)-like extratropical atmospheric variability, and can act as a bridge (or conduit) through which North Pacific extratropical atmospheric variability influences ENSO. Consequently, the VM shares some resemblance with the PMM. However, the VM and PMM differ in terms of their spatial structure, temporal variations, and impacts on ENSO. In contrast to the local SST mode of the PMM in the subtropical northeast Pacific, the VM, as a basin-scale SST mode of the North Pacific basin, includes large-amplitude SSTAs over the northeast Pacific, the western North Pacific (WNP), and the high-latitude North Pacific. Results indicate that SLP anomalies associated with the VM are generally located west of those associated with the PMM. In addition, the VM has a unique temporal variability, independent of the PMM. Furthermore, the VM is more closely linked to ENSO than is the PMM, possibly because the VM combines the effects of the PMM and SSTAs in the WNP. Thus, the VM represents a more reliable precursor signal than the PMM for ENSO events and may have profound implications for ENSO prediction.