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Manuel Pulido and John Thuburn

circulation from the summer to the winter hemisphere. This circulation explains the high temperatures observed in the winter mesosphere. Lindzen (1981) realized that an isotropic gravity wave spectrum generated at tropospheric levels would be filtered in a systematic way by the background wind in the middle atmosphere leading to a systematic forcing by gravity waves in the upper stratosphere and lower mesosphere. The seasonal variation of gravity wave drag (GWD) produced by gravity wave filtering deduced

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Charles McLandress and Theodore G. Shepherd

seen in surface pressure and storm tracks. Thus, possible changes in SSWs resulting from climate change would have an effect on ozone recovery and on Arctic ozone more generally. Because chemistry climate models (CCMs) are the only tools available for predicting the future evolution of climate change and ozone recovery in the middle atmosphere, it is important that they be able to get the SSWs right. Charlton et al. (2007) intercompared six stratosphere-resolving models and found that most

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Andrew Orr, Peter Bechtold, John Scinocca, Manfred Ern, and Marta Janiskova

1. Introduction The middle atmosphere is dominated by a westerly jet in the winter hemisphere, an easterly jet in the summer hemisphere, and a meridional circulation comprised of upwelling in the tropics and downwelling over the winter pole, referred to as the Brewer–Dobson circulation ( Brewer 1949 ). The Brewer–Dobson circulation is a mechanically driven circulation arising from midlatitude wintertime wave drag in the stratosphere associated primarily with the dissipation of planetary

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Chengyun Yang, Tao Li, Anne K. Smith, and Xiankang Dou

midlatitude troposphere, a signature of the MJO extending into the middle atmosphere might be expected. However, up to now, the response of the Southern Hemisphere (SH) middle atmosphere to the MJO has not been well studied. The MJO is, on average, weaker during the austral winter than the boreal winter ( Wang and Rui 1990 ; Hendon and Salby 1994 ). However, variability in the middle atmosphere is also weaker in the austral winter than in the boreal winter so the MJO-induced variation has the potential

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V. I. Fomichev, A. I. Jonsson, J. de Grandpré, S. R. Beagley, C. McLandress, K. Semeniuk, and T. G. Shepherd

1. Introduction The observed increase in atmospheric CO 2 concentrations represents the single most significant anthropogenic perturbation to the climate system. Most attention naturally focuses on the associated warming effects in the troposphere. In the middle atmosphere, the enhanced infrared emission associated with the CO 2 increase acts instead to cool the region, particularly at the stratopause where the temperature maximizes. Indeed, a cooling of the middle atmosphere in recent

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William Randel, Petra Udelhofen, Eric Fleming, Marvin Geller, Mel Gelman, Kevin Hamilton, David Karoly, Dave Ortland, Steve Pawson, Richard Swinbank, Fei Wu, Mark Baldwin, Marie-Lise Chanin, Philippe Keckhut, Karin Labitzke, Ellis Remsberg, Adrian Simmons, and Dong Wu

1. Introduction Climatological datasets for the middle atmosphere are useful for empirical studies of climate and variability, and are also necessary for constraining the behavior of numerical models. Current general circulation model (GCM) simulations routinely extend into the middle atmosphere (model tops at 50 km or higher), and require observational datasets for validation (e.g., Pawson et al. 2000 ). A number of middle-atmosphere climatologies have been developed in the research community

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Bodil Karlsson and Maartje Kuilman

1. Introduction Ultraviolet radiation interacts strongly with atoms and molecules in the upper part of the middle atmosphere, making this region particularly sensitive to changes in the solar irradiance. Above about 100 km, in the thermosphere, the direct effect of the solar flux has the dominating influence on the temperature field. In the mesosphere, on the other hand, the breaking of gravity waves (GWs) drives the circulation ( Lindzen 1981 ) in a way that makes adiabatic processes dominate

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Jason Goodman and John Marshall

) and McCartney et al. (1997) . Frankignoul (1985) concisely reviews middle-latitude atmosphere–ocean interactions. Many researchers suggest the atmosphere generates the climate variations on its own, and the ocean reacts passively to that stimulus. Some modeling studies (e.g., James and James 1989 ) show that a model atmosphere is capable, in the presence of fixed surface boundary conditions (fixed ocean), of exhibiting long-term persistent (climate) states, in clear contradiction to the usual

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Charles McLandress and Theodore G. Shepherd

1. Introduction Recent simulations using comprehensive middle atmosphere models predict an increase in the Brewer–Dobson circulation (BDC) in response to climate change, as diagnosed by changes in lower stratospheric tropical upwelling ( Butchart et al. 2000 ; Butchart and Scaife 2001 ; Sigmond et al. 2004 ; Butchart et al. 2006 ; Fomichev et al. 2007 ; Li et al. 2008 ; Garcia and Randel 2008 ). This increase is due to an increase in wave drag in the extratropical stratosphere, as

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D. Rind, N. K. Balachandran, and R. Suozzo

VOLUME 5JOURNAL OF CLIMATEMARCH 1992D. RIND, N. K. BALACHANDRAN,* AND R. Suozzo* *Goddard Space Flight Center, Inst it ute for Space Studies, New York, New York(Manuscript received 26 December 1990, in final form 26 June 1991)ABSTRACTThe effects of volcanic aerosols on the middle atmosphere are investigated with the Goddard Institute forSpace Studies (GISS) Global Climate/Middle Atmosphere model. Volcanic aerosols with a visible optical depthof 0.15 are put into the lower stratosphere, and

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