Improving the Predictability of Two Types of ENSO by the Characteristics of Extratropical Precursors

Abstract

The Central Pacific (CP) and Eastern Pacific (EP) types of El Niño-Southern Oscillation events are distinctly different in terms of their forming locations and mechanisms. Using an updated physical-base statistical forecast model, the forecast of CP indices has overall higher skills than that of EP indices due to the higher persistent forecast skill. At lead time beyond 6-month, the predictability of CP indices can be greatly enhanced by including the extratropical precursor from the North Pacific, confirming the ocean-atmosphere interaction associated with North Pacific Oscillation (NPO)/Victoria Mode (VM) evolution. The predictability of EP indices can be moderately enhanced by including the extratropical precursor from the south, resulting from the charging of the equatorial Pacific. We also find that the predictability of CP indices does not significantly decrease after 2000 while the predictability of EP indices drops dramatically, suggesting the strengthening impacts of NPO/VM on the CP-ENSO in the recent two decades.