Inter‐Hemispheric Coupling During Sudden Stratospheric Warming Events With Elevated Stratopause

Athreyas, Kashyapa Naren; García, Rolando R.; Chandran, Amal

doi:10.1029/2020jd033761

Cited by 3 publications

(8 citation statements)

References 37 publications

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“…It is also worth noting that warm anomalies greater than 2 K are observed in the southern upper mesosphere around z = 80 km in 40°S-90°S. This feature is consistent with the IHC associated with the Arctic SSW indicated by previous studies (e.g., Karlsson, McLandress, et al, 2009;Naren Athreyas et al, 2022;Yasui et al, 2021).…”

Section: Time-height Section Of Zonal-mean Zonal Windsupporting

confidence: 90%

“…Such a remote response is inferred to be caused by the modulation of the meridional circulation, driven by wave forcing and its interaction with the mean flow over the two hemispheres (e.g., Körnich & Becker, 2010; Murphy et al., 2012; Naren Athreyas et al., 2022; Yasui et al., 2021). Körnich and Becker (2010), hereafter referred to as KB10, proposed a simple and compelling scenario for the IHC and demonstrated it using an axisymmetric model that included gravity wave (GW) parameterizations.…”

Section: Introductionmentioning

confidence: 99%

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Interhemispheric Coupling Study by Observations and Modelling (ICSOM): Concept, Campaigns, and Initial Results

et al. 2023

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An international joint research project, entitled Interhemispheric Coupling Study by Observations and Modelling (ICSOM), is ongoing. In the late 2000s, an interesting form of interhemispheric coupling (IHC) was discovered: when warming occurs in the winter polar stratosphere, the upper mesosphere in the summer hemisphere also becomes warmer with a time lag of days. This IHC phenomenon is considered to be a coupling through processes in the middle atmosphere (i.e., stratosphere, mesosphere, and lower thermosphere). Several plausible mechanisms have been proposed so far, but they are still controversial. This is mainly because of the difficulty in observing and simulating gravity waves (GWs) at small scales, despite the important role they are known to play in middle atmosphere dynamics. In this project, by networking sparsely but globally distributed radars, mesospheric GWs have been simultaneously observed in seven boreal winters since 2015/16. We have succeeded in capturing five stratospheric sudden warming events and two polar vortex intensification events. This project also includes the development of a new data assimilation system to generate long-term reanalysis data for the whole middle atmosphere, and simulations by a state-of-the-art GW-permitting general circulation model using the reanalysis data as initial values. By analyzing data from these observations, data assimilation, and model simulation, comprehensive studies to investigate the mechanism of IHC are planned. This paper provides an overview of ICSOM, but even initial results suggest that not only GWs but also large-scale waves are important for the mechanism of the IHC.

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Section: Time-height Section Of Zonal-mean Zonal Windsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Interhemispheric Coupling Study by Observations and Modelling (ICSOM): Concept, Campaigns, and Initial Results

et al. 2023

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“…In the case of UA-ICON, the 25 km threshold results in too few ESEs and therefore we reduced this threshold to 18 km. Nevertheless, even with the reduced threshold, we found approximately two ESEs per decade in UA-ICON (CTL simulation) which is less than the observed frequency of ESEs (3.5 events per decade in MLS observations (Naren Athreyas et al, 2022)). The annual frequency of ESEs was reported between 28% and 36% in four 53-year simulations by WACCM .…”

Section: Analysis Methodscontrasting

confidence: 77%

“…For example, Manney et al (2008) have shown that MERRA reanalyses are unable to capture the rise of the stratopause to very high altitudes during ESEs. With the improvements in the spatial and temporal resolutions of middle and upper atmospheric satellite data, detailed analyses of ESEs have become feasible in recent years (France, Harvey, Alexander, et al, 2012;Manney et al, 2008;Naren Athreyas et al, 2022;Orsolini et al, 2010;Shi et al, 2022). Modeling studies with WACCM (France & Harvey, 2013;Limpasuvan et al, 2016;Orsolini et al, 2017), the Canadian Middle Atmosphere Model (CMAM; McLandress et al, 2013), a high-resolution middle atmosphere GCM developed for the KANTO project (Tomikawa et al, 2012), the ECHAM/MESSy Atmospheric Chemistry (EMAC; Scheffler et al, 2022) and with the Japanese Atmospheric General circulation model for Upper Atmosphere Research (JAGUAR, Okui et al (2021)) provided insights into the sequence of events associated with the occurrence of a typical ES event.…”

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confidence: 99%

The Climatology of Elevated Stratopause Events in the UA‐ICON Model and the Contribution of Gravity Waves

et al. 2023

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The upper boundary of the stratosphere, the stratopause, is sensitive to the increasing concentrations of greenhouse gases (GHG) and is considered an independent and novel indicator of GHG-induced climate change (Olivero & Thomas, 2001;Pisoft et al., 2021;Rind et al., 1998). Both space-and ground-based observations indicate a robust stratospheric temperature decrease of about 1-3 K over the last four decades ( -2018( , Steiner et al. (2020a), including a near-global cooling near the stratopause (Steiner et al., 2020b). Associated with such a temperature decrease, Pisoft et al. ( 2021) estimated a global decrease in stratopause height and stratospheric thickness for the future climate under increasing concentration of GHG. Stratopause height trends are crucial to correctly understand and attribute changes in dynamics and tracer transport, and moreover, they may affect satellite orbits (Schrøder et al., 2007). It is therefore of interest to study the characteristics of the stratopause (e.g., its height and temperature) and understand the mechanisms influencing it. While in low and mid-latitudes, the

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“…Athreyas et al. (2022) further found that during major SSW events with elevated stratopause, the polar summer mesopause cools during the stratospheric warming phase and warms during the stratopause discontinuity and reformation phases.…”

Section: Introductionmentioning

confidence: 97%

Southern Hemisphere Response to the Secondary Planetary Waves Generated During the Arctic Sudden Stratospheric Final Warmings: Influence of the Quasi‐Biennial Oscillation

Qin

Dou

et al. 2022

JGR Atmospheres

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Based on the Modern‐Era Retrospective analysis for Research and Applications version 2 reanalysis and Aura Microwave Limb Sounder geopotential height observations, the anomalously strong secondary planetary waves (PWs) with westward zonal wavenumber 1 and periods of 10–16 days are unexpectedly captured in the Southern (summer) Hemisphere (SH) during the Arctic sudden stratospheric final warmings (SSFWs) in 2015 and 2022, while no distinct secondary PW signal occurs in the SH during the 2005, 2014, and 2016 Arctic SSFWs. The Eliassen‐Palm (EP) flux diagnostics show that the secondary PWs during the 2015 and 2022 SSFWs have strong trans‐equatorial components at ∼35–60 km, but the southward EP flux from the Northern Hemisphere during the other three SSFWs decays dramatically around the equator. Further diagnostic results on the background conditions indicate that the phase of the quasi‐biennial oscillation (QBO) in the middle stratosphere plays a crucial role in the SH response to the secondary PW during SSFW. The strong equatorial westward winds at ∼32–42 km result in the critical layers and negative waveguides for the secondary W1 PW during the 2005, 2014, and 2016 SSFWs, which significantly block the trans‐equatorial propagation of PW. Such PW suppression is not observed during the 2015 and 2022 SSFWs since the middle stratospheric QBO is in the eastward phase. Moreover, the strong secondary PW in the SH during the 2015 and 2022 SSFWs can additionally induce the poleward residual circulation to facilitate the mesospheric total residual circulation transition from summer pattern to winter pattern in the SH.

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Inter‐Hemispheric Coupling During Sudden Stratospheric Warming Events With Elevated Stratopause

Cited by 3 publications

References 37 publications

Interhemispheric Coupling Study by Observations and Modelling (ICSOM): Concept, Campaigns, and Initial Results

Interhemispheric Coupling Study by Observations and Modelling (ICSOM): Concept, Campaigns, and Initial Results

The Climatology of Elevated Stratopause Events in the UA‐ICON Model and the Contribution of Gravity Waves

Southern Hemisphere Response to the Secondary Planetary Waves Generated During the Arctic Sudden Stratospheric Final Warmings: Influence of the Quasi‐Biennial Oscillation

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