Tropical Stratospheric Forcings Weaken the Response of the East Asian Winter Temperature to ENSO

The El Niño–Southern Oscillation (ENSO) plays a critical role in predicting the winter surface temperature over East Asia. Numerous studies have attempted to improve the seasonal forecasting skill in view of the combined effects of ENSO and oceanic–tropospheric factors. However, high uncertainty and notable challenges still exist in using the ENSO to predict the surface temperature. Here, we showed that tropical stratospheric forcings (Quasi-Biennial Oscillation, QBO) could disrupt the response of the surface temperature to ENSO. The response of the East Asian surface temperature to El Niño/La Niña events evidently weakened in winter during the westerly/easterly phase of the QBO. This disruption has shown an increasing trend in recent decades, limiting the usefulness of ENSO alone as a seasonal predictor of the surface temperature. The modulation of the QBO on the East Asian surface temperature is achieved mainly by affecting subtropical zonal winds and North Pacific wave activity. Our analyses suggest that the QBO is a nonnegligible predictor in improving seasonal forecasts of the East Asian surface temperature, even comparable to the ENSO.