Variation in the Holton–Tan effect by longitude

Abstract

The teleconnection between the Quasi-Biennial Oscillation (QBO) and the boreal winter polar vortex, the Holton-Tan effect, is analyzed in the Whole Atmosphere Community Climate Model (WACCM) with a focus on how stationary wave propagation varies by QBO phase. These signals are difficult to isolate in reanalyses because of large internal variability in short observational records, especially when decomposing the data by QBO phase. A 1,500-year ensemble is leveraged by defining the QBO index at five different isobars between 10 and 70 hPa. The Holton-Tan effect is a robust part of the atmospheric response to the QBO in WACCM with warming of the polar stratosphere during easterly QBO (QBOE). A nudging technique is used to reduce polar stratospheric variability in one simulation. This enables isolation of the impact of the QBO on the atmosphere in the absence of a polar stratospheric response to the QBO: referred to as the "direct effect" and the polar stratospheric response, "indirect effect." This simulation reveals that the polar stratospheric warming during QBOE pushes the tropospheric jet equatorward, opposing the poleward shift of the jet by the QBOE, especially over the North Pacific. The Holton-Tan effect varies over longitude. The QBO induces stronger planetary wave forcing to the mean flow in the extratropical lower stratosphere between Indonesia and Alaska. The North Pacific polar stratosphere responds to this before other longitudes. What follows is a shift in the position of the polar vortex toward Eurasia (North America) during easterly (westerly) QBO. This initiates downstream planetary wave responses over North America, the North Atlantic, and Siberia. This spatiotemporal evolution is found in transient simulations in which QBO nudging is "switched on." The North Pacific lower stratosphere seems more intrinsically linked to the QBO while other longitudes appear more dependent on the mutual interaction between the QBO and polar stratosphere.

Quantifying stratospheric biases and identifying their potential sources in subseasonal forecast systems

“…In turn, the QBO has the ability to modulate the tropospheric jet streams, tropical convection, and other phenomena such as the Madden-Julian Oscillation (e.g., Gray et al, 2018;Anstey et al, 2021, and references therein). These tropospheric teleconnections of the QBO are known to affect the NAO, as well as surface temperatures and precipitation near East Asia and in the tropics on both seasonal-mean and subseasonal timescales (Anstey et al, 2021;Gray et al, 2018;Haynes et al, 2021;Elsbury et al, 2021;Park et al, 2022). The QBO also has an apparent influence on the strength of the polar vortex, particularly in the Northern Hemisphere (NH), whereby easterly or westerly winds in the tropical lower stratosphere tend to lead to a weaker or stronger polar vortex, respectively (e.g., Holton and Tan, 1980;Calvo et al, 2007;Garfinkel et al, 2012;Anstey and Shepherd, 2014;Gray et al, 2018;Rao et al, 2020a).…”

CMIP6 Models Underestimate the Holton‐Tan Effect

“…During December, PV ϕ weakens in the middle stratosphere between 30°N and 50°N, suggesting that the upward and equatorward propagating planetary waves that ordinarily enter this region from the extratropics during winter are inhibited ‐ the waves are confined to higher latitudes (Figure 2b). PV ϕ steepens lower in the mid‐latitude stratosphere (∼530 K), supporting more upward planetary wave propagation, particularly over the North Pacific (Elsbury et al., 2021). During January, the polar stratospheric PV ϕ weakens and this signal moves downward in time (Figure 2c).…”

“…Fewer studies consider the zonally asymmetric response to the QBO during winter. We have done this for the lower stratosphere (Elsbury et al, 2021). Hamilton et al (2004) and Hitchman and Huesmann (2009) have done this for the middle stratosphere.…”

“…Fewer studies consider the zonally asymmetric response to the QBO during winter. We have done this for the lower stratosphere (Elsbury et al., 2021). Hamilton et al.…”

Effect of the Quasi‐Biennial Oscillation on the Madden Julian Oscillation Teleconnections in the Southern Hemisphere

“…The difference in the strength of the wave trains may be due to differences in the background flow. The background flow during QBOW may be more conducive to wave propagation than for QBOE as under QBOW the zonal flow is displaced poleward, whereas for QBOE it is displaced equatorward (e.g., Elsbury et al., 2021). Differences in the basic state zonal flow have been suggested as influencing the position of the MJO teleconnections in the Northern Hemisphere (e.g., Jenney et al., 2021; Toms et al., 2020).…”