On the forcings of the unusual Quasi-Biennial Oscillation structure in February 2016

Li, Haiyan; Kedzierski, Robin Pilch; Matthes, Katja

doi:10.5194/acp-20-6541-2020

Cited by 12 publications

(13 citation statements)

References 47 publications

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“…3c of Lin et al (2019). This result is also consistent with the findings of Li et al (2020), who showed the contribution of strong Kelvin wave activity related to an El Niño event to the long-lasting westerly jet near 20 hPa. MRG waves ( Fig.…”

Section: General Characteristics Of Zonal Wind and Equatorial Wavessupporting

confidence: 91%

“…2) during the disruption. The enhanced Kelvin wave activity during the disruption period was caused by the enhanced convective activity associated with strong El Niño events (Li et al, 2020). Overall, we found that convectively coupled equatorial waves are enhanced during the QBO disruption, which seem to be associated with El Niño.…”

Section: Contributions Of Rossby Waves and Mrg Wavesmentioning

confidence: 57%

“…Based on the classical theory, the QBO is generated by momentum deposition by vertically propagating equatorial planetary and gravity waves (Lindzen and Holton, 1968;Holton and Lindzen, 1972). The impact of the QBO is not limited to the tropical stratosphere; the QBO modulates the strength of tropospheric convection (Collimore et al, 2003;Liess and Geller, 2012;Lee et al, 2019), Madden-Julian oscillation (Yoo and Son, 2016;Marshall et al, 2017), and the tropical cyclone tracks (Ho et al, 2009). In addition, the QBO affects not only the subtropical jet and the subsequent changes in the growth and life cycle of the synoptic-to planetary-scale waves in the troposphere (Garfinkel and Hartmann, 2011), but also the intensity of the stratospheric polar vortex (Holton and Tan, 1980;Anstey and Shepherd, 2014), which is strongly tied to the surface temperature and pressure distribution in the extratropics Kidston et al, 2015;Gray et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…This is the first study to classify equatorial waves in detail and investigate each wave's role in the QBO disruption. Note that if the EPD is calculated without separating each wave mode, the importance of the westward-propagating waves might be obscured by the eastward-propagating waves, given that Kelvin wave activity was enhanced during the 2015/16 QBO disruption (Kumar et al, 2018;Li et al, 2020). The second new aspect of this study is to investigate the role of smallscale CGWs.…”

Section: Introductionmentioning

confidence: 99%

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Role of equatorial waves and convective gravity waves in the 2015/16 quasi-biennial oscillation disruption

2020

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Abstract. In February 2016, the descent of the westerly phase of the quasi-biennial oscillation (QBO) was unprecedentedly disrupted by the development of easterly winds. Previous studies have shown that extratropical Rossby waves propagating into the deep tropics were the major cause of the 2015/16 QBO disruption. However, a large portion of the negative momentum forcing associated with the disruption still stems from equatorial planetary and small-scale gravity waves, which calls for detailed analyses by separating each wave mode compared with climatological QBO cases. Here, the contributions of resolved equatorial planetary waves (Kelvin, Rossby, mixed Rossby–gravity (MRG), and inertia–gravity (IG) waves) and small-scale convective gravity waves (CGWs) obtained from an offline CGW parameterization to the 2015/16 QBO disruption are investigated using MERRA-2 global reanalysis data from October 2015 to February 2016. In October and November 2015, anomalously strong negative forcing by MRG and IG waves weakened the QBO jet at 0–5∘ S near 40 hPa, leading to Rossby wave breaking at the QBO jet core in the Southern Hemisphere. From December 2015 to January 2016, exceptionally strong Rossby waves propagating horizontally (vertically) continuously decelerated the southern (northern) flank of the jet. In February 2016, when the westward CGW momentum flux at the source level was much stronger than its climatology, CGWs began to exert considerable negative forcing at 40–50 hPa near the Equator, in addition to the Rossby waves. The enhancement of the negative wave forcing in the tropics stems mostly from strong wave activity in the troposphere associated with increased convective activity and the strong westerlies (or weaker easterlies) in the troposphere, except that the MRG wave forcing is more likely associated with increased barotropic instability in the lower stratosphere.

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Section: General Characteristics Of Zonal Wind and Equatorial Wavessupporting

confidence: 91%

Section: Contributions Of Rossby Waves and Mrg Wavesmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Role of equatorial waves and convective gravity waves in the 2015/16 quasi-biennial oscillation disruption

2020

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“…In addition, sudden stratospheric warmings (SSWs) and quasi-biennial oscillation (QBO) events can dynamically couple the entire atmosphere from the lower atmosphere to the ionosphere (Li et al, 2020;Yamazaki et al, 2020;Yadav et al, 2019;Matthias and Ern, 2018;Stray et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Eastward-propagating planetary wave in the polar middle atmosphere

Tang

Dou

2021

Preprint

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Abstract. We presented the global variations of the eastward propagating wavenumber 1 (E1), 2 (E2), 3 (E3), and 4 (E4) planetary waves (PWs) and their diagnostic results in the polar middle atmosphere, using MERRA-2 temperature and wind datasets in 2019. It is clearly shown that the eastward wave modes exist during winter periods with westward background wind in both hemispheres. The maximum wave amplitudes in the southern hemisphere (SH) are slightly larger and lie lower than those in the northern hemisphere (NH). It is also found that the wave perturbations peak at lower latitudes with smaller amplitude as the wavenumber increases. The period of the E1 mode varies from 3 to 5 days in both hemispheres, while the period of E2 mode is slightly longer in the NH (48 h) than in the SH (40 h). The periods of the E3 are ~30 h in both SH and NH, and the period of E4 is ~24 h. Though the wave periods become shorter as the wavenumber increases, their mean phase speeds are relatively stable, which are ~53, ~58, ~55, and ~52 m/s at 70° latitudes for W1, W2, W3, and W4, respectively. The eastward PWs occur earlier with increasing zonal wavenumber, which agrees well with the seasonal variations of the background zonal wind through the generation of critical layers. Diagnostic analysis also shows that the mean flow instability in the upper stratosphere and upper mesosphere may both contribute to the amplification of the eastward PWs.

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A revisit and comparison of the quasi-biennial oscillation (QBO) disruption events in 2015/16 and 2019/20

Wang,

Rao,

et al. 2023

Atmospheric Research

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On the forcings of the unusual Quasi-Biennial Oscillation structure in February 2016

Cited by 12 publications

References 47 publications

Role of equatorial waves and convective gravity waves in the 2015/16 quasi-biennial oscillation disruption

Role of equatorial waves and convective gravity waves in the 2015/16 quasi-biennial oscillation disruption

Eastward-propagating planetary wave in the polar middle atmosphere

A revisit and comparison of the quasi-biennial oscillation (QBO) disruption events in 2015/16 and 2019/20

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