Zonal Asymmetry of the QBO Temperature Signal in the Tropical Tropopause Region

Tegtmeier, Susann; Anstey, James; Davis, Sean; Ivanciu, Ioana; Jia, Yue; McPhee, D. Landon; Kedzierski, Robin Pilch

doi:10.1029/2020gl089533

Cited by 17 publications

(25 citation statements)

References 48 publications

(71 reference statements)

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“…To better illustrate the longitudinal characteristics of the W

-

E differences (Tegtmeier et al ., 2020a), in Figure 9 we show scatter plots of the tropopause pressure anomalies as a function of the QBO amplitude at 70 hPa. For simplicity, the amplitude is defined as the range of the deseasonalized QBO index (i.e.,

{U}_{\mathrm{EQ}}^{\mathrm{range}}={U}_{\mathrm{EQ}}^{\mathrm{max}}-{U}_{\mathrm{EQ}}^{\mathrm{min}}

).…”

Section: Resultsmentioning

confidence: 99%

The impact of the QBO on the region of the tropical tropopause in QBOi models: Present‐day simulations

Serva

Anstey²,

Bushell

et al. 2022

Quart J Royal Meteoro Soc

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The processes occurring in the tropical tropopause layer (TTL) are of great importance for stratosphere–troposphere exchanges and the variability of the Earth's climate. Previous studies demonstrated the increasing ability of atmospheric general circulation models (AGCMs) in simulating the TTL, depending on factors such as the horizontal and vertical resolution, with the major role for physical parametrizations. In this work we assess the mean state and variability of the tropical upper troposphere and lower stratosphere simulated by 13 AGCMs of the Stratosphere–troposphere Processes And their Role in Climate Quasi‐Biennial Oscillation initiative (QBOi) for the historical period. As these models internally generate quasi‐biennial oscillations (QBOs) of the stratospheric zonal wind, we can analyse the simulated QBO influence on the TTL on interannual time‐scales. We find that model biases in temperature near the tropopause are strongly related to water vapour concentrations in the lower stratosphere. A source of intermodel spread derives from stratospheric aerosols, as the responses to eruptions differ between those models prescribing volcanic aerosol forcing. The QBO influence on the thermal structure is generally realistic in the equatorial region, but the subtropical response is weak compared with the reanalysis. This is associated with a limited downward penetration of QBO winds, generally smaller QBO meridional widths, and weaker temperature anomalies, which disappear above the tropopause for most models. We discuss the QBO impacts on tropopause pressure and precipitation, characterized by large uncertainties due to the small signal in the observational records and sampling uncertainty. Realistic QBO connection with the troposphere in some models suggests that the underlying physical processes can be correctly simulated. Overall, we find that the QBOi models have limited ability to reproduce the observed modulation of the TTL processes, which is consistent with biases in the vertical and latitudinal extent of the simulated QBOs degrading this connection.

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“…To better illustrate the longitudinal characteristics of the W

-

{U}_{\mathrm{EQ}}^{\mathrm{range}}={U}_{\mathrm{EQ}}^{\mathrm{max}}-{U}_{\mathrm{EQ}}^{\mathrm{min}}

).…”

Section: Resultsmentioning

confidence: 99%

The impact of the QBO on the region of the tropical tropopause in QBOi models: Present‐day simulations

Serva

Anstey²,

Bushell

et al. 2022

Quart J Royal Meteoro Soc

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show abstract

“…Future work could explore how this tidally locked ozone chemistry would interact with oscillations in dayside production of ozone through stratospheric photochemistry. In addition, LASO-related temperature anomalies in our simulation reach 40-50 K (∼25% deviation from the mean), while the QBO of temperature on Earth is limited to 1-2 K (Tegtmeier et al 2020). Large variations in air temperature will also potentially affect measurements of thermal emission spectra from the atmosphere.…”

Section: Oscillations In Meteorological and Atmospheric Compositionmentioning

confidence: 83%

Longitudinally Asymmetric Stratospheric Oscillation on a Tidally Locked Exoplanet

Cohen

Bollasina

Palmer

et al. 2022

ApJ

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Using a three-dimensional general circulation model, we show that the atmospheric dynamics on a tidally locked Earth-like exoplanet, simulated with the planetary and orbital parameters of Proxima Centauri b, support a longitudinally asymmetric stratospheric wind oscillation (LASO), analogous to Earth’s quasi-biennial oscillation (QBO). In our simulations, the LASO has a vertical extent of 35–55 km, a period of 5–6.5 months, and a peak-to-peak wind speed amplitude of −70 to +130 m s−1 with a maximum at an altitude of 41 km. Unlike the QBO, the LASO displays longitudinal asymmetries related to the asymmetric thermal forcing of the planet and to interactions with the resulting stationary Rossby waves. The equatorial gravity wave sources driving the LASO are localized in the deep convection region at the substellar point and in a jet exit region near the western terminator, unlike the QBO, for which these sources are distributed uniformly around the planet. Longitudinally, the western terminator experiences the highest wind speeds and undergoes reversals earlier than other longitudes. The antistellar point only experiences a weak oscillation with a very brief, low-speed westward phase. The QBO on Earth is associated with fluctuations in the abundances of water vapor and trace gases such as ozone, which are also likely to occur on exoplanets if these gases are present. Strong fluctuations in temperature and the abundances of atmospheric species at the terminators will need to be considered when interpreting atmospheric observations of tidally locked exoplanets.

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“…Future work could explore how this tidally locked ozone chemistry would interact with oscillations in dayside production of ozone through stratospheric photochemistry. In addition, LASOrelated temperature anomalies in our simulation reach 40-50 K (∼ 25% deviation from the mean), while the QBO of temperature on Earth is limited to 1-2 K (Tegtmeier et al 2020). Large variations in air temperature will also potentially affect measurements of thermal emission spectra from the atmosphere.…”

Section: Oscillations In Meteorological and Atmospheric Compositionmentioning

confidence: 84%

Longitudinally asymmetric stratospheric oscillation on a tidally locked exoplanet

Cohen,

Bollasina,

Palmer

et al. 2021

Preprint

View full text Add to dashboard Cite

Using a three-dimensional general circulation model, we show that the atmospheric dynamics on a tidally locked Earth-like exoplanet, simulated with the planetary and orbital parameters of Proxima Centauri b, support a longitudinally asymmetric stratospheric wind oscillation (LASO), analogous to Earth's quasi-biennial oscillation (QBO). In our simulations, the LASO has a vertical extent of 35-55 km, a period of 5-6.5 months, and a peak-to-peak wind speed amplitude of -70 to +130 ms −1 with a maximum at an altitude of 41 km. Unlike the QBO, the LASO displays longitudinal asymmetries related to the asymmetric thermal forcing of the planet and to interactions with the resulting stationary Rossby waves. The equatorial gravity wave sources driving the LASO are localised in the deep convection region at the substellar point and in a jet exit region near the western terminator, unlike the QBO, for which these sources are distributed uniformly around the planet. Longitudinally, the western terminator experiences the highest wind speeds and undergoes reversals earlier than other longitudes. The antistellar point only experiences a weak oscillation with a very brief, low-speed westward phase. The QBO on Earth is associated with fluctuations in the abundances of water vapour and trace gases such as ozone which are also likely to occur on exoplanets if these gases are present. Strong fluctuations in temperature and the abundances of atmospheric species at the terminators will need to be considered when interpreting atmospheric observations of tidally locked exoplanets.

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Zonal Asymmetry of the QBO Temperature Signal in the Tropical Tropopause Region

Cited by 17 publications

References 48 publications

The impact of the QBO on the region of the tropical tropopause in QBOi models: Present‐day simulations

The impact of the QBO on the region of the tropical tropopause in QBOi models: Present‐day simulations

Longitudinally Asymmetric Stratospheric Oscillation on a Tidally Locked Exoplanet

Longitudinally asymmetric stratospheric oscillation on a tidally locked exoplanet

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