Multidecadal Variation in the Seasonal Predictability of Winter PNA and Its Sources

Based on reanalysis and ensemble hindcasts data, this work investigates the multidecadal variation in the seasonal predictability of the Pacific-North American (PNA) teleconnection pattern during the winter and its sources. The results show that at the two ends of the 20th century, the PNA is mostly driven by the El Nino-Southern Oscillation (ENSO), and a good seasonal prediction of the PNA is expected if models can accurately predict the PNA-ENSO relationship. During the middle 20th century, the PNA is not only driven by ENSO but also closely linked to the Pacific Decadal Oscillation through the air-sea coupling process in the extratropical North Pacific. Improvements in the seasonal prediction of the PNA require models to accurately predict both the PNA-ENSO relationship and the air-sea coupling in the northern extratropical Pacific.