An evaluation of tropical waves and wave forcing of the QBO in the QBOi models

Holt, Laura; Lott, François; García, Rolando R.; Kiladis, George N.; Cheng, Yuan-Ming; Anstey, James; Braesicke, Peter; Bushell, Andrew C.; Butchart, Neal; Cagnazzo, Chiara; Chen, Chih‐Chieh; Chun, Hye‐Yeong; Kawatani, Yoshio; Kerzenmacher, Tobias; Kim, Young‐Ha; McLandress, C.; Naoe, Hiroaki; Osprey, Scott; Richter, Jadwiga H.; Scaife, Adam A.; Scinocca, John; Serva, Federico; Versick, Stefan; Watanabe, Shingo; Yoshida, Kohei; Yukimoto, Seiji

doi:10.1002/qj.3827

Cited by 44 publications

(74 citation statements)

References 76 publications

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“…A much better QBO was obtained in a previous version of this model, CESM1‐WACCM, when the vertical resolution was doubled in the troposphere and lower stratosphere (Garcia & Richter, ). Holt et al () has demonstrated a clear relationship between the wave forcing from resolved waves in the lower stratosphere and vertical resolution in QBOi models. Similar dependence of lower stratospheric wave forcing on horizontal resolution was not found.…”

Section: Summary and Discussionmentioning

confidence: 98%

“…Similar dependence of lower stratospheric wave forcing on horizontal resolution was not found. Holt et al () also showed that even models that have ample wave momentum flux entering the lower stratosphere seem to underestimate the contribution of these waves to the QBO driving in the upper stratosphere, which suggests that factors such as vertical resolution and numerical dissipation might influence the effectiveness of Kelvin and mixed Rossby GWs in driving the QBO.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Since the resolved wave forcing of the QBO is underestimated in most models, GCMs typically depend on parameterizations of nonorographic GW drag to account for the rest of the forcing (Bushell et al, ; Holt et al, ). The majority of models utilize GW parameterizations that use a fixed GW source spectrum that is the same in the tropics and extratropics and is not explicitly linked to spatiotemporally varying tropospheric sources.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…As part of QBOi, simulations of the QBO were examined in 13 atmosphere‐only models run under present‐day climate (Bushell et al, ), and 11 models' QBO response to doubling and quadrupling CO 2 was examined by Richter et al (). In addition, the proximal forcing of the QBO was examined by Holt et al (). Modeling centers participating in QBOi were attentive to the representation of their models stratosphere, and the simulation of the QBO in particular.…”

Section: Introductionmentioning

confidence: 99%

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Progress in Simulating the Quasi‐Biennial Oscillation in CMIP Models

et al. 2020

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The quasi-biennial oscillation (QBO) of the zonal mean zonal wind is the primary mode of variability in the tropical lower stratosphere. The QBO is characterized by alternating easterly westerly shear layers that descend down from ∼10 to 100 hPa. The QBO is also seen in lower stratospheric tropical temperature, water vapor, and ozone and affects tropospheric variability through various teleconnections. We examine here the progress in simulating the QBO in the Coupled Model Intercomparison Project (CMIP) models, more specifically in CMIP3, CMIP5, and CMIP6 models. We show that the number of models that are able to simulate the QBO has increased from 0 in CMIP3, to 5 in CMIP5, to 15 in CMIP6. While the number of models with an internally generated QBO has tripled from CMIP5 to CMIP6, the fidelity of the simulation averaged over the CMIP models has not improved. We show that CMIP5 and CMIP6 models represent the QBO period and latitudinal extent quite well; however the QBO amplitude is shifted upwards relative to observations resulting in large underestimation of QBO amplitude at all levels below 20 hPa. The underestimation of QBO amplitude in the lowermost stratosphere and lack of variations downward to the tropopause and below will likely impact the quality of teleconnections seen in the current generation Earth system models. Plain Language SummaryThe quasi-biennial oscillation (QBO) is an important mode of variability in the tropical lower stratosphere and impacts variability in the stratosphere and troposphere. We show that the number of climate or Earth system models being able to simulate the QBO in Coupled Model Intercomparison Project (CMIP) models has increased by a factor of 3 from CMIP5 to CMIP6. However, the quality of the simulation of the QBO has not improved. Overall, models simulate the period of the QBO well but underestimate the QBO amplitude at all levels below 20 hPa. Key Points:• The number of models with a QBO has tripled from CMIP5 to CMIP6 • The mean period of the QBO is well represented in CMIP5 and CMIP6 models • CMIP5 and CMIP6 models generally are deficient in representing the QBO amplitude at all levels below 20 hPa

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Section: Summary and Discussionmentioning

confidence: 98%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Progress in Simulating the Quasi‐Biennial Oscillation in CMIP Models

et al. 2020

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“…Weaknesses in gravity wave parameterization methods may be partly to blame. Evidence suggests that increasing model vertical resolution improves the simulation of the QBO (Giorgetta et al, 2002;Richter et al, 2014), because resolved tropical wave drag increases at higher vertical resolution (Holt et al, 2016(Holt et al, , 2020. These resolved waves may include Kelvin waves, mixed Rossby-gravity waves, and inertia-gravity waves.…”

Section: Introductionmentioning

confidence: 99%

Balloon‐Borne Observations of Short Vertical Wavelength Gravity Waves and Interaction With QBO Winds

Vincent

Alexander

2020

JGR Atmospheres

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The quasi‐biennial oscillation (QBO), a ubiquitous feature of the zonal mean zonal winds in the equatorial lower stratosphere, is forced by selective dissipation of atmospheric waves that range in periods from days to hours. However, QBO circulations in numerical models tend to be weak compared with observations, probably because of limited vertical resolution that cannot adequately resolve gravity waves and the height range over which they dissipate. Observations are required to help quantify wave effects. The passage of a superpressure balloon (SPB) near a radiosonde launch site in the equatorial Western Pacific during the transition from the eastward to westward phase of the QBO at 20 km permits a coordinated study of the intrinsic frequencies and vertical structures of two inertia‐gravity wave packets with periods near 1 day and 3 days, respectively. Both waves have large horizontal wavelengths of about 970 and 5,500 km. The complementary nature of the observations provided information on their momentum fluxes and the evolution of the waves in the vertical. The near 1 day westward propagating wave has a critical level near 20 km, while the eastward propagating 3‐day wave is able to propagate through to heights near 30 km before dissipation. Estimates of the forcing provided by the momentum flux convergence, taking into account the duration and scale of the forcing, suggests zonal force of about 0.3–0.4 m s−1 day−1 for the 1‐day wave and about 0.4–0.6 m s−1 day−1 for the 3‐day wave, which acts for several days.

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Equatorial waves, diurnal tides and small-scale thermal variability in the tropical lower stratosphere from COSMIC-2 radio occultation

Randel

2020

Preprint

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

show abstract

An evaluation of tropical waves and wave forcing of the QBO in the QBOi models

Cited by 44 publications

References 76 publications

Progress in Simulating the Quasi‐Biennial Oscillation in CMIP Models

Progress in Simulating the Quasi‐Biennial Oscillation in CMIP Models

Balloon‐Borne Observations of Short Vertical Wavelength Gravity Waves and Interaction With QBO Winds

Equatorial waves, diurnal tides and small-scale thermal variability in the tropical lower stratosphere from COSMIC-2 radio occultation

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