Intensified ENSO Teleconnection to Extratropical Winter Climate Variabilities after Mid-1990s and Seasonal Prediction

Abstract:

This study examines intensified ENSO teleconnection to the Arctic Oscillation (AO) and the East Asian Winter Monsoon (EAWM) after mid-1990s. These represent enhanced influence of tropics to extratropical climate variability. Seasonal prediction skill of each climate variability is assessed with state-of-the-art dynamical ensemble prediction systems (EPSs): CanCM3, CanCM4, CFSv2, CM2.1, and GEOS-5, which are affiliated in the North American National multi-model ensemble (NMME). Most of prediction systems show higher seasonal prediction skill of the AO during the recent period (1997–2010) than that of the earlier period (1983–1996) with strengthened relationship between ENSO and the AO. The recent intensification is associated with a low frequency Pacific SST variability such as the North Pacific Gyre Oscillation (NPGO). On the other hand, the EAWM also shows strengthened relationship with ENSO after mid-1990s. Several prediction systems, which can reproduce their recent intensified relationship, show more useful prediction skill than the other prediction systems without the strong ENSO-EAWM relationship. These results imply recent seasonal prediction skills of the AO and the EAWM are possibly associated with external forcing in the tropics. In this regard, we can improve seasonal prediction of the AO and the EAWM by understanding physical mechanism and improving model reproducibility of the teleconnection.