Response of the Quasi‐Biennial Oscillation to Historical Volcanic Eruptions

Abstract

It is well-appreciated that large tropical eruptions impact the atmosphere. Injected sulfate aerosols cool the surface and warm the lower stratosphere through absorption of shortwave radiation (Robock, 2000). The impacts of this forcing on the troposphere and extratropical stratosphere have received a great deal of attention, including: an acceleration of the polar vortex (e.g., Graf et al., 1993), changes to planetary waves (e.g., Stenchikov et al., 2002), a reduction in global precipitation (e.g., Iles et al., 2013), and altered surface temperatures (e.g., Robock & Mao, 1995) including winter warming. However, the in situ impact of volcanic aerosols on the Quasi-Biennial Oscillation (QBO) has received much less attention. Some studies have considered geoengineering and supereruptions, which impact the tropical stratosphere on longer timescales than more moderately sized eruptions. The general finding is that aerosol heating leads to anomalous westerlies, consistent with thermal wind balance (Randel et al., 1999), despite the large Rossby number at low latitudes. Aquila et al. (2014) simulated geoengineering as a time-invariant aerosol forcing and found that sufficiently large 2 SO Einjections could lengthen or shutdown the QBO in a westerly state, moderated by changes in upwelling. Niemeier and Schmidt (2017) explored a wider variety of forcing scenarios and obtained similar results, noting a dependence on initial QBO phase for transport. Richter et al. ( 2017) also obtained similar results, finding that interactive chemistry apparently buttressed the QBO against an aerosol-driven shutdown. Lastly, Brenna et al. ( 2021) simulated the supereruption of Los Chocoyos (75,000 years before present) and found a more complex response, with a long easterly pause followed by a westerly pause.Hence, the transient impact on the QBO from more moderately sized eruptions is not clear a priori, and it appears that little work has been done on the subject. This is the focus of our study. Capturing the correct QBO response after an eruption is important for seasonal prediction (e.g., Garfinkel et al., 2018), QBO teleconnections (e.g., Marshall & Scaife, 2009), and trace gases (e.g., Tweedy et al., 2017). It is also desirable

The Influence of Internal Climate Variability on Stratospheric Water Vapor Increases After Large‐Magnitude Explosive Tropical Volcanic Eruptions

“…This result is very different from many previous findings using models in which an intensified BDC was shown (e.g., Abalos et al., 2015; Aquila et al., 2013; DallaSanta et al., 2021; Kinne et al., 1992; Pitari, 1993; Pitari & Mancini, 2002; Toohey et al., 2014). However, Garfinkel et al.…”

“…This result is very different from many previous findings using models in which an intensified BDC was shown (e.g., Abalos et al, 2015;Aquila et al, 2013;DallaSanta et al, 2021;Kinne et al, 1992;Pitari, 1993;Pitari & Mancini, 2002;Toohey et al, 2014). However, Garfinkel et al (2017) and Garcia et al (2011) found the post-volcanic BDC response was an acceleration effect, but mainly in the mid and upper stratosphere, and Garfinkel et al (2017) showed very little change in the BDC in the lower stratosphere (see their Figure 6b).…”

“…The slowdown in tropical upwelling occurs as a result of a decrease in wave forcing in the subtropics diagnosed by the anomalous EP flux divergence (Figure S7 in Supporting Information ). Meanwhile, the vertical stability of the atmosphere is enhanced in the tropical lower stratosphere (Figure S8 in Supporting Information ), which also acts to reduce tropical upwelling (DallaSanta et al., 2021). Together these results indicate an overall deceleration of the tropical upwelling in response to the volcanic eruption.…”

Impacts, processes and projections of the quasi-biennial oscillation

“…Low-latitude volcanic eruptions (FIG. 1b) are another: aerosol-induced heating warms the tropical lower stratosphere and drives increased upwelling, biasing the QBO toward increased eastward shear and modulating its period, although the exact response depends on the QBO phase at the time of the eruption [151,152]. The response of modelled QBOs to stratospheric sulfate geoengineering is qualitatively similar but model-dependent in its details, as well as depending on the magnitude and latitude of aerosol injection [153][154][155][156].…”

Stratospheric water vapor and ozone response to different QBO disruption events in 2016 and 2020

“…In January 2016 and 2020, the anomalous QBO westerlies in the tropical lower stratosphere were unexpectedly interrupted by anomalous QBO easterlies caused by planetary waves propagating from the mid-latitudes toward the equatorial region combined with equatorial convective gravity waves (Osprey et al, 2016;Coy et al, 2017;Kang et al, 2020;Kang and Chun, 2021). There is not yet a clear understanding of how these QBO disruptions are linked to anomalously warm or cold sea surface temperatures (Taguchi, 2010;Schirber, 2015;Dunkerton, 2016;Christiansen et al, 2016;Barton and McCormack, 2017), volcanic aerosols (Kroll et al, 2020;DallaSanta et al, 2021), wildfire smoke (Khaykin et al, 2020;Yu et al, 2021;Peterson et al, 2021) and climate changes (Anstey et al, 2021b). However, recent study based on climate model simulations from phase six of the Coupled Model Intercomparison Project (CMIP6) predicts increased disruption frequencies to the quasi-regular QBO cycle in a changing climate (Osprey et al, 2016;Anstey et al, 2021b).…”