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William J. M. Seviour, Steven C. Hardiman, Lesley J. Gray, Neal Butchart, Craig MacLachlan, and Adam A. Scaife

coupling of the stratosphere to the troposphere ( Black and McDaniel 2007 ). The predictability of these events was investigated in GloSea5, but not found to be highly significant. This is probably because the mean timing of the final warming is toward the end of the 4-month hindcast simulation (around 20 November at 10 hPa), and the final warming does not occur before the end of the hindcast for some ensemble members, thereby introducing a bias in the mean. b. Ozone depletion GloSea5 does not include

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Laurence Armi and Georg J. Mayr

controlled flow: The top of the cloud layer in the WCR image ( Fig. 2b ) descends continuously from 6.0 km MSL upstream to 5.5 km MSL above the crest and 4.9 km MSL at the separation downstream. The height of the top of the cloud-filled layer measured relative to the crest at 3.85 km MSL is 2.15 km upstream and 1.65 km at the crest, giving the two-thirds ratio. Fig . 3. Vertical sections along tracks shown in Fig. 1a from the King Air (below 9 km; troposphere) and G-V (stratosphere) with reflectivity

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Rei Ueyama, Edwin P. Gerber, John M. Wallace, and Dargan M. W. Frierson

45°N. These parameter settings have been shown to produce realistic troposphere–stratosphere coupling ( Gerber and Polvani 2009 ) and a realistic BDC ( Gerber 2012 ). The reader is referred to these papers for a more detailed description of the model. The 6-hourly global European Centre for Medium-Range Weather Forecasts Interim Re-Analysis (ERA-Interim; Dee et al. 2011 ) data are analyzed for the 32-yr period from 1 January 1979 to 31 December 2010. The data are gridded at 1.5° latitude by 1

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Lantao Sun, Gang Chen, and Walter A. Robinson

zonal wind deceleration ( Black and McDaniel 2007b ), in the stratospheric wave drag and residual vertical circulation ( McLandress et al. 2010 ), and in the downward wave coupling between the stratosphere and the troposphere ( Shaw et al. 2010 ; Harnik et al. 2011 ). On interannual time scales, SFW events are observed to influence the seasonal transition of the tropospheric circulation, advancing or delaying it 1 or 2 weeks ( Black et al. 2006 ; Black and McDaniel 2007b ). These observational

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Diane J. Ivy, Susan Solomon, and David W. J. Thompson

1. Introduction The apparent propagation of some polar circulation anomalies from the stratosphere to the troposphere during winter and spring has been noted for about a half-century ( Julian and Labitzke 1965 ; Quiroz 1977 ), and has been the subject of intense study since it was shown to be robust in composite analyses by Baldwin and Dunkerton (2001) . Stratosphere–troposphere dynamical coupling was first observed in the Arctic on a seasonal basis in winter, where circulation anomalies in

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Oliver Watt-Meyer and Paul J. Kushner

decomposition of the wavenumber–frequency spectrum into standing and traveling parts, calculate analytic expressions for the variance of each component and their covariance, and show how the decomposition can be used to reconstruct standing and traveling wave fields. While the techniques that we describe are quite general, we were motivated to carry out this analysis by particular issues related to wave-driven stratosphere–troposphere coupling in the Northern Hemisphere extratropics ( Baldwin and Dunkerton

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Charles Chemel, Maria R. Russo, John A. Pyle, Ranjeet S. Sokhi, and Cornelius Schiller

1. Introduction The characteristics of the upper-troposphere/lower-stratosphere (UT/LS) region are intrinsically determined by those of both spheres. The balance of processes that regulate its dynamical, radiative, and chemical characteristics is at the heart of the debate on UT/LS exchanges. In particular, the quantification of the respective role of convective overturning in the troposphere and radiative and/or diabatic overturning in the stratosphere in determining the entry of atmospheric

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Hiromasa Ueda, Tetsuo Fukui, Mizuo Kajino, Mitsuaki Horiguchi, Hiroyuki Hashiguchi, and Shoichiro Fukao

1. Introduction Diffusion processes in the free atmosphere play an important role in the transport of momentum, heat, and mass on global and regional scales, although the eddy diffusivity there is much smaller than that in the atmospheric boundary layer. In particular, diffusion processes of minor constituents in the upper troposphere and lower stratosphere are essential to global warming, stratospheric ozone depletion, and transboundary air pollution problems because they govern the exchange

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Kerry Emanuel, Susan Solomon, Doris Folini, Sean Davis, and Chiara Cagnazzo

-equilibrium hypothesis of Raymond (1995) , the convective and large-scale downdrafts into the subcloud layer must, on average, balance surface enthalpy fluxes in order that there are no large tendencies of entropy in the subcloud layer. Assuming that both convective downdrafts and large-scale subsidence into the subcloud layer both transport a value of moist static energy characteristic of the middle troposphere, Emanuel (1995) showed that the updraft mass flux is given by where is the large-scale vertical

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Peter Hitchcock and Theodore G. Shepherd

1. Introduction The Arctic polar vortex is one of the most variable components of the zonal-mean circulation of the atmosphere on intraseasonal to interannual time scales. The radiatively generated vortex is disrupted intermittently and irregularly by planetary-scale Rossby waves produced by the troposphere below. In the most spectacular cases, these bursts result in major stratospheric sudden warmings, during which the zonal-mean westerly winds reverse. For up to 3 months following roughly

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