Relationship between the stratospheric quasi-biennial oscillation and tropospheric circulation in northern autumn

Abstract

[1] This study examines the influence of stratospheric quasi-biennial oscillation (QBO) on the polar vortex (hereafter referred to as Holton-Tan relationship) in the Northern Hemisphere (NH) and investigates the mechanism of the Holton-Tan relationship, such as its beginning process and its interaction between the equatorial QBO and the tropospheric circulation, focusing on the connections between the QBO and the tropospheric circulation in the NH autumn. The National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis (NCEP/NCAR) and NCEP-DOE Reanalysis II data sets are used in the analysis over a 25 year period from September 1980 to February 2005. In the zonally averaged field, easterly (westerly) anomalies at high latitudes (50°N–75°N), westerly (easterly) anomalies at midlatitudes (around 30°N–50°N), and easterly (westerly) anomalies at subtropical latitudes (around 10°N–30°N) are present, extending vertically throughout the atmosphere in NH autumn (September–November) during the easterly (westerly) phase of the QBO. The composite difference in the Eliassen-Palm (EP) flux divergence is consistent with observed mean flow tendencies near the tropopause in midlatitude and high-latitude stratosphere in autumn, indicating that atmospheric waves play a crucial role in the formation of zonal wind anomalies. The Holton-Tan relationship also begins to appear around late October and becomes clearer with intraseasonal March. There are significant vertical velocity anomalies from the troposphere through the lower stratosphere at low and middle latitudes in association with the convergence anomalies of the EP flux when the QBO is in the easterly phase. These results suggest that the stratospheric QBO is connected with tropospheric circulation through wave activities and the associated meridional circulation in NH autumn.