QBO modulation of the semiannual oscillation in MAECHAM5 and HAMMONIA

Peña‐Ortiz, Cristina; Schmidt, Hauke; Giorgetta, Marco; Keller, Martin

doi:10.1029/2010jd013898

Cited by 23 publications

(36 citation statements)

References 37 publications

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“…Therefore the descent of the SAO westward wind phase with time is usually much steeper than the descent of the SAO eastward wind phase, which is mainly driven by vertically propagating waves. In particular, several studies suggest that the filtering of the spectrum of upward-propagating waves by the QBO has a strong influence on the SAO winds (e.g., Hirota, 1980;Garcia et al, 1997;Peña-Ortiz et al, 2010). This wave-filtering effect of the QBO (mainly critical-level filtering) is also seen in observed gravity wave momentum flux spectra .…”

Section: Introductionmentioning

confidence: 78%

“…In most simulations, the SAO is driven by a combination of resolved waves and parameterization of subgridscale gravity waves (e.g., Orr et al, 2010;Peña-Ortiz et al, 2010;Osprey et al, 2010). In some simulations, the SAO is driven alone by gravity waves and planetary waves explicitly resolved by the model (e.g., Kawatani et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…This filtering of waves is relevant for the formation of circulation patterns at higher altitudes. For example, the pre-filtered wave spectrum is likely responsible for the formation of a QBO and an SAO in the tropical mesopause region (see also Dunkerton, 1982;Burrage et al, 1996;Baldwin et al, 2001;Richter and Garcia, 2006;Peña-Ortiz et al, 2010;de Wit et al, 2013;Kishore Kumar et al, 2014, and references therein). It has also been found that the QBO and the SAO interact with each other.…”

Section: Introductionmentioning

confidence: 99%

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Driving of the SAO by gravity waves as observed from satellite

Ern¹,

Preusse²,

Riese³

2015

Ann. Geophys.

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Abstract. It is known that atmospheric dynamics in the tropical stratosphere have an influence on higher altitudes and latitudes as well as on surface weather and climate. In the tropics, the dynamics are governed by an interplay of the quasi-biennial oscillation (QBO) and semiannual oscillation (SAO) of the zonal wind. The QBO is dominant in the lower and middle stratosphere, and the SAO in the upper stratosphere/lower mesosphere. For both QBO and SAO the driving by atmospheric waves plays an important role. In particular, the role of gravity waves is still not well understood.In our study we use observations of the High Resolution Dynamics Limb Sounder (HIRDLS) satellite instrument to derive gravity wave momentum fluxes and gravity wave drag in order to investigate the interaction of gravity waves with the SAO. These observations are compared with the ERA-Interim reanalysis. Usually, QBO westward winds are much stronger than QBO eastward winds. Therefore, mainly gravity waves with westward-directed phase speeds are filtered out through critical-level filtering already below the stratopause region. Accordingly, HIRDLS observations show that gravity waves contribute to the SAO momentum budget mainly during eastward wind shear, and not much during westward wind shear. These findings confirm theoretical expectations and are qualitatively in good agreement with ERA-Interim and other modeling studies. In ERAInterim most of the westward SAO driving is due to planetary waves, likely of extratropical origin. Still, we find in both observations and ERA-Interim that sometimes westwardpropagating gravity waves may contribute to the westward driving of the SAO. Four characteristic cases of atmospheric background conditions are identified. The forcings of the SAO in these cases are discussed in detail, supported by gravity wave spectra observed by HIRDLS. In particular, we find that the gravity wave forcing of the SAO cannot be explained by critical-level filtering alone; gravity wave saturation without critical levels being reached is also important.

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Driving of the SAO by gravity waves as observed from satellite

Ern¹,

Preusse²,

Riese³

2015

Ann. Geophys.

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“…Sometimes, even three vertically aligned QBO phases can be identified (Pascoe 2005). Corresponding correlations were found, e.g., in simulations with the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) of Peña-Ortiz et al (2010) (referred to as PO10).…”

Section: Introductionmentioning

confidence: 87%

“…Such models were used to study the vertical coupling between stratosphere and mesosphere for the QBO (Kawatani et al 2010;Kawatani and Hamilton 2013;Richter et al 2014), the SAO (Peña-Ortiz et al 2010;Smith 2012), and SSWs (Liu and Roble 2002;Harada et al 2010;Richter et al 2010;Miller et al 2013;Zülicke and Becker 2013).…”

Section: Introductionmentioning

confidence: 99%

Relation between Equatorial Mesospheric Wind Anomalies during Spring and Middle Atmosphere Variability Modes

Zülicke

Becker

2017

SOLA

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Strong easterly wind anomalies in the equatorial upper mesosphere were observed during northern hemispheric spring equinox. While the anomalies are mainly related to the semi-annual oscillation (SAO) in the stratopause region and to the quasi-biennial oscillation (QBO) in the stratosphere, an additional influence of sudden stratospheric warmings (SSWs) was recently suggested. In order to analyze this relation, we use an 18-year simulation of the Kühlungsborn Mechanistic Circulation Model (KMCM) that includes these middle atmosphere variability modes. We compute composites for the different phases of the QBO and intensities of SSWs. The results support the notion that easterly equatorial mesospheric wind anomalies occur during spring equinox if the QBO is in its westerly phase. In addition we show that this relation does not hold when the preceding winter is characterized by strong SSWs. We interpret this phenomenon as a result of a persistent strengthening of the residual circulation in the equatorial stratopause region.(Citation: Zülicke, C., and E. Becker, 2017: Relation between equatorial mesospheric wind anomalies during spring and middle atmosphere variability modes. SOLA, 13A, 31−35,

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Interannual variability of mesopause zonal winds over Ascension Island: Coupling to the stratospheric QBO

et al. 2013

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[1] Zonal-wind measurements obtained between October 2001 and July 2011 with the SKiYMET meteor radar located at Ascension Island (8 ı S, 14 ı W) have been used to study the interannual variability at meteor ablation altitudes (approximately 78-100 km) and its coupling to the stratospheric quasi-biennial oscillation (QBO). An upper mesospheric QBO (MQBO) with a period of 27.5 months has been detected throughout the observational period. The MQBO is found to be out-of-phase with the stratospheric QBO (SQBO) at 15-20 hPa and in-phase compared to 70 hPa, whereas no significant zero time-lag correlation exists between the long-term mesospheric zonal winds and the SQBO at 40-50 hPa. The MQBO magnitude is found to be 4.1˙0.7 m/s at 88 km. No significant change in MQBO magnitude is found throughout the altitude range under consideration. It was found that the MQBO signal is mainly carried around the March equinox, although the MQBO signal is present throughout most of the year, although less pronounced, at the lower altitudes as well. No observational evidence was found that the MQBO, between approximately 78-100 km, plays a role in the interhemispheric ducting of the quasi-16 day wave.

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QBO modulation of the semiannual oscillation in MAECHAM5 and HAMMONIA

Cited by 23 publications

References 37 publications

Driving of the SAO by gravity waves as observed from satellite

Driving of the SAO by gravity waves as observed from satellite

Relation between Equatorial Mesospheric Wind Anomalies during Spring and Middle Atmosphere Variability Modes

Interannual variability of mesopause zonal winds over Ascension Island: Coupling to the stratospheric QBO

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