Compensation between Resolved and Unresolved Wave Driving in the Stratosphere: Implications for Downward Control

Cohen, Naftali Y.; Gerber, Edwin P.; Bühler, Oliver

doi:10.1175/jas-d-12-0346.1

Cited by 79 publications

(101 citation statements)

References 39 publications

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“…Recently, some studies revealed possible compensation of PW drag of the middle atmospheric circulation by parameterized OGWs in general circulation models (McLandress and McFarlane 1993;Cohen et al 2013Cohen et al , 2014Sigmond and Shepherd 2014;Watson and Gray 2015). Our results show that taking account of OGW parameterization can both decrease or increase wave amplitudes, EP-fluxes, and wave drag of the mean flow depending on the considered PW modes.…”

Section: Discussionmentioning

confidence: 57%

Simulating influences of QBO phases and orographic gravity wave forcing on planetary waves in the middle atmosphere

et al. 2015

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Recently developed parameterization of stationary orographic gravity waves (OGWs) generated by the Earth's topography was implemented into a general circulation model of the middle and upper atmosphere. We performed numerical simulations of the zonal mean wind and amplitudes of stationary planetary waves and normal atmospheric modes with periods of 4-16 days at altitudes from the troposphere to the lower thermosphere in January for easterly and westerly phases of the quasi-biennial oscillation (QBO) including and excluding the stationary OGW parameterization. Simulations show that accounting dynamical and thermal effects of stationary OGWs can lead to substantial changes (up to 50-90 %) in the amplitudes of stationary planetary waves. Amplitudes of westward travelling normal atmospheric modes change (up to 50-90 %) at different altitudes and latitudes of the northern hemisphere due to OGW effects. Transitions from the easterly to westerly QBO phases can change planetary wave amplitudes up to ±30-90 % at middle and high latitudes. These changes in PW amplitudes are consistent with distributions of EP-flux and refractive index under different QBO phases simulated including our parameterization of stationary OGWs.

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Section: Discussionmentioning

confidence: 57%

Simulating influences of QBO phases and orographic gravity wave forcing on planetary waves in the middle atmosphere

et al. 2015

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“…However, this ratio differs largely between various models. Cohen et al (2013) suggest that due to compensation effects between the different wave types, the impact of the differences in gravity wave perturbation on the total circulation is reduced. Hence, models tend to agree more on the total strength of the circulation than on individual components.…”

Section: Model Characteristics That Can Influence Mixingmentioning

confidence: 99%

Quantifying the effect of mixing on the mean age of air in CCMVal-2 and CCMI-1 models

et al. 2018

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Abstract. The stratospheric age of air (AoA) is a useful measure of the overall capabilities of a general circulation model (GCM) to simulate stratospheric transport. Previous studies have reported a large spread in the simulation of AoA by GCMs and coupled chemistry-climate models (CCMs). Compared to observational estimates, simulated AoA is mostly too low. Here we attempt to untangle the processes that lead to the AoA differences between the models and between models and observations. AoA is influenced by both mean transport by the residual circulation and two-way mixing; we quantify the effects of these processes using data from the CCM inter-comparison projects CCMVal-2 (Chemistry-Climate Model Validation Activity 2) and CCMI-1 (Chemistry-Climate Model Initiative, phase 1). Transport along the residual circulation is measured by the residual circulation transit time (RCTT). We interpret the difference between AoA and RCTT as additional aging by mixing. Aging by mixing thus includes mixing on both the resolved and subgrid scale. We find that the spread in AoA between the models is primarily caused by differences in the effects of mixing and only to some extent by differences in residual circulation strength. These effects Published by Copernicus Publications on behalf of the European Geosciences Union. are quantified by the mixing efficiency, a measure of the relative increase in AoA by mixing. The mixing efficiency varies strongly between the models from 0.24 to 1.02. We show that the mixing efficiency is not only controlled by horizontal mixing, but by vertical mixing and vertical diffusion as well. Possible causes for the differences in the models' mixing efficiencies are discussed. Differences in subgrid-scale mixing (including differences in advection schemes and model resolutions) likely contribute to the differences in mixing efficiency. However, differences in the relative contribution of resolved versus parameterized wave forcing do not appear to be related to differences in mixing efficiency or AoA.

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confidence: 99%

Quantifying the effect of mixing on the mean Age of Air in CCMVal-2 and CCMI-1 models

Dietmüller¹,

Eichinger²,

Garny³

et al. 2017

Preprint

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Abstract. Stratospheric age of air (AoA) is a useful measure of the overall capabilities of a general circulation model (GCM) to simulate stratospheric transport. Previous studies have reported a large spread in the simulation of AoA by GCMs and coupled chemistry-climate models (CCMs). Compared to observational estimates simulated AoA is mostly too low. Here we attempt to untangle the processes that lead to the AoA differences between the models and between models and observations. AoA is influenced by both, mean transport along the residual circulation and two-way mixing; we quantify the effects of these 5 processes using data from the CCM inter-comparison projects CCMVal-2 and CCMI-1. Transport along the residual circulation is measured by the residual circulation transit time (RCTT). We interpret the difference between AoA and RCTT as additional aging by mixing. Aging by mixing thus includes mixing on both the resolved and subgrid scale. We find that the spread inAoA between the models is primarily caused by differences in the effects of mixing, and only to some extent by differences in residual circulation strength. These effects are quantified by the mixing efficiency, a measure of the relative increase of AoA by only controlled by horizontal mixing, but by vertical mixing and vertical diffusion as well. Possible causes for the differences in the models' mixing efficiencies are discussed. Differences in subgrid scale mixing (including differences in advection schemes and model resolutions) likely contribute to the differences in mixing efficiency. However, differences in the relative contribution of resolved versus parametrized wave forcing do not appear to be related to differences in mixing efficiency or AoA.

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Compensation between Resolved and Unresolved Wave Driving in the Stratosphere: Implications for Downward Control

Cited by 79 publications

References 39 publications

Simulating influences of QBO phases and orographic gravity wave forcing on planetary waves in the middle atmosphere

Simulating influences of QBO phases and orographic gravity wave forcing on planetary waves in the middle atmosphere

Quantifying the effect of mixing on the mean age of air in CCMVal-2 and CCMI-1 models

Quantifying the effect of mixing on the mean Age of Air in CCMVal-2 and CCMI-1 models

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