Modulation of the Quasi-Biennial Oscillation on the East Asian Surface Air Temperature in Boreal Winter

Abstract

Abstract This study analyzes the response of East Asian surface air temperature (SAT) to the quasi-biennial oscillation (QBO) in boreal winter using the JRA-55 reanalysis dataset and the CAM6 model. East Asian SAT patterns in response to the boreal winter QBO vertical profile are derived from singular value decomposition (SVD) analysis. The leading mode of SVD (SVD1) shows an evident cold center over East Asia, while warm and cold centers show an east–west dipole in the second mode of SVD (SVD2). The corresponding QBO pattern in SVD1 has two opposite centers, with an upper-stratospheric easterly phase and a lower-stratospheric westerly phase; however, there is only one middle-stratospheric westerly center in SVD2. The SVD1-like QBO tends to cause more significant East Asian SAT anomalies than the SVD2-like QBO pattern. This difference originates from the response of the stratospheric polar vortex and the North Pacific circulation to the QBO. The SVD1-like QBO forces a cyclonic anomaly over the midlatitude North Pacific and an anticyclonic anomaly over China via a subtropical path and polar path, leading to a zonal pressure gradient and meridional wind anomaly over East Asia. Temperature advection driven by this meridional wind affects cooling and warming over East Asia. By contrast, there are no significant responses to the SVD2-like QBO over the midlatitude North Pacific, and thus, the corresponding East Asian SAT response is weak. Significance Statement East Asian surface air temperature (SAT) variation is often attributed to variations in lower-atmospheric dynamics and sea surface temperature. Few studies focus on the role of the QBO. In this study, we diagnose the influence of the stratospheric QBO on East Asian SAT during boreal winter. Both reanalysis and simulated results indicate that the response of East Asian SAT is sensitive to the selection of multilevel QBO indices. This sensitivity comes from the changes in QBO’s subtropical and polar influencing path. Our results provide a new perspective on East Asian SAT changes.