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Peter Hitchcock, Theodore G. Shepherd, and Shigeo Yoden

1. Introduction Radiative transfer plays an important role in damping temperature perturbations in the middle atmosphere. In general, this damping is a nonlocal process in which heat is transferred to and from remote levels of the atmosphere and the surface and radiated away to space. This process is also nonlinear, mostly as a result of the nonlinear dependence of radiated power on temperature. In the mesosphere, molecular collisions occur sufficiently infrequently that local thermodynamic

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Ryosuke Yasui, Kaoru Sato, and Yasunobu Miyoshi

1. Introduction Sudden stratospheric warming (SSW) events often occur in the polar region in Northern Hemisphere (NH) winter. This is a phenomenon in which a meridional circulation in the stratosphere is driven by stationary Rossby wave (RW) forcing, resulting in adiabatic heating in the polar stratosphere and adiabatic cooling in the equatorial stratosphere (e.g., Matsuno 1971 ). Interhemispheric coupling (IHC) of the middle atmosphere, which is described by an anticorrelation between the

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Simon P. Alexander, Kaoru Sato, Shingo Watanabe, Yoshio Kawatani, and Damian J. Murphy

1. Introduction Despite their relatively small scale, gravity waves are an important component of the atmospheric general circulation because they transfer momentum upward from tropospheric sources to the middle atmosphere. The gravity wave drag generated upon breaking closes the mesospheric jet and induces a summer-to-winter-pole mesospheric circulation ( Haynes et al. 1991 ; Garcia and Boville 1994 ). Gravity waves, together with planetary waves, drive the winter polar stratosphere away from

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Kaoru Sato, Satoshi Tateno, Shingo Watanabe, and Yoshio Kawatani

much different from that expected by radiation: the summer polar upper mesosphere is the coldest place in the earth’s atmosphere because of the upward motion, leading to the formation of polar mesospheric clouds. The polar stratospheric clouds that appear in the polar winter are confined to the cold lower stratosphere because the middle and upper stratosphere in winter is warm owing to the downward motion. Gravity waves are primary waves that drive the meridional circulation in the summer and

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Fabrizio Sassi, R. R. Garcia, D. Marsh, and K. W. Hoppel

1. Introduction Coupled atmosphere–ocean climate models, and in particular most of those that have been used in the Intergovernmental Panel on Climate Change (IPCC) reports, typically have a poorly resolved middle atmosphere, and chemical composition is for the most part specified ( Solomon et al. 2007 ). These models cannot represent ozone depletion or the complex couplings associated with changes of chemical composition and their effects on the dynamical and thermal structure of the middle

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Scott M. Osprey, Lesley J. Gray, Steven C. Hardiman, Neal Butchart, Andrew C. Bushell, and Tim J. Hinton

operational analysis data were obtained from the British Atmospheric Data Centre ( ). S. Osprey and L. Gray were supported by the NERC National Centre for Atmospheric Science (NCAS) Climate directorate; N. Butchart and S. C. Hardiman were supported by the Joint DECC and Defra Integrated Climate Programme–DECC/Defra (GA01101). REFERENCES Andrews , D. G. , J. R. Holton , and C. B. Leovy , 1987 : Middle Atmosphere Dynamics . Academic Press, 489 pp . Baldwin , M. P. , and T

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Yoshio Kawatani, Kevin Hamilton, Lesley J. Gray, Scott M. Osprey, Shingo Watanabe, and Yousuke Yamashita

impacts the troposphere as well as the lower stratosphere. This raises the question of how much the inclusion of a well-resolved middle atmosphere changes weather and climate simulations in numerical models. Studies as early as Boville and Cheng (1988) have investigated the effects of the stratosphere on representations of tropospheric phenomena within global circulation models. More recently Sassi et al. (2010) discussed simulations using the “low top” standard Community Atmosphere Model, version

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Kaoru Sato, Takenari Kinoshita, and Kota Okamoto

1. Introduction Material circulation of the middle atmosphere is essentially driven by the momentum deposition of atmospheric waves such as gravity waves and Rossby waves propagating from the troposphere as well as the diabatic heating by radiative processes, while differential latent and sensible heatings are also important for the tropospheric circulation. The circulation in the mesosphere forms one cell with a meridional flow from the high latitudes of the summer hemisphere to the high

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Yoshio Kawatani, Jae N. Lee, and Kevin Hamilton

production in the middle atmosphere. The chemical source in the water vapor mass mixing ratio tendency equation is expressed as , where k is a rate (specified as a function of pressure), Q is a parameter set at 4.25 × 10 −6 (corresponding to 6.8 ppmv), and q is the model H 2 O mass mixing ratio [see ECMWF (2013) for more details and references therein]. Our T106 MIROC AGCM integrations reported in this paper were conducted with annually repeating sea surface temperatures (SSTs) based on present

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Yoshio Kawatani, Kevin Hamilton, Kaoru Sato, Timothy J. Dunkerton, Shingo Watanabe, and Kazuyoshi Kikuchi

, . 10.1002/qj.637 Andrews , D. G. , J. R. Holton , and C. B. Leovy , 1987 : Middle Atmosphere Dynamics . Academic Press, 489 pp . Baldwin , M. P. , and Coauthors , 2001 : The quasi-biennial oscillation . Rev. Geophys. , 39 , 179 – 229 , . 10.1029/1999RG000073 Barton , C. A. , and J. P. McCormack , 2017 : Origin of the 2016 QBO disruption and its relationship to extreme El Niño events . Geophys. Res. Lett

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