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Joowan Kim and Seok-Woo Son

1. Introduction In the tropics, the thermal boundary between the stratosphere and troposphere is well defined by the coldest level, the so-called cold-point tropopause (CPT). Thermal characteristics of the CPT have been extensively examined as they play a crucial role in stratosphere–troposphere coupling and exchange ( Holton et al. 1995 ). For instance, transport of water vapor from the troposphere to the stratosphere is to a great extent controlled by temperature at the CPT. Because the air

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Murry L. Salby and Patrick F. Callaghan

1. Introduction In the tropical stratosphere, the circulation is dominated by the quasi-biennial oscillation (QBO) of equatorial wind. In the tropical troposphere, it is characterized by the Hadley circulation, which is forced by convection and the release of latent heat. Historically, these two circulations have been regarded as independent. In the classical theory of the QBO, the stratospheric circulation depends upon the tropospheric circulation only indirectly, through vertically

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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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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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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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Kazuaki Nishii, Hisashi Nakamura, and Yvan J. Orsolini

1. Introduction It is well established that a stratospheric sudden warming (SSW), which is characterized by abrupt warming in the polar stratosphere, is induced by enhanced upward propagation of planetary waves (PWs) from the troposphere ( Matsuno 1971 ). Many previous case studies on SSWs have pointed out that a tropospheric blocking high (BH), which gives rise to persistent anomalous meanders of tropospheric jets and abnormal weather conditions, can contribute to the enhancement of upward PW

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Gloria L. Manney, Michaela I. Hegglin, William H. Daffer, Michael J. Schwartz, Michelle L. Santee, and Steven Pawson

vortex that may extend into the lowermost stratosphere, McIntyre (1995) ] play an important role in coupling the stratospheric and tropospheric circulations. In addition to the upper tropospheric jets’ role in forcing stratospheric disturbances, the structure of the stratospheric vortex is critical to wave coupling between the stratosphere and troposphere (e.g., Harnik et al. 2011 ). Climate model simulations indicate that the effects of the upper tropospheric–lower stratospheric (UTLS) jets on

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Ying Li and Ngar-Cheung Lau

studies (e.g., Garfinkel et al. 2010 ; Kolstad et al. 2010 ; Kolstad and Charlton-Perez 2011 ) and is shown to be almost identical to the NAM index based on the EOF analysis. The index used in our study is also more effective than zonal wind speed at 60°N for studying the stratosphere–troposphere coupling ( Baldwin and Thompson 2009 ). A negative anomaly in our vortex strength index corresponds to anomalously low heights and a strong vortex, whereas a positive anomaly implies a weak vortex. The

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Daniela I. V. Domeisen, Amy H. Butler, Kristina Fröhlich, Matthias Bittner, Wolfgang A. Müller, and Johanna Baehr

, and the descent of stratospheric perturbations into the lower troposphere. J. Climate, 26, 4725–4748 , doi: 10.1175/JCLI-D-12-00581.1 . Luo , J.-J. , S. Masson , E. Roeckner , G. Madec , and T. Yamagata , 2005 : Reducing climatology bias in an ocean–atmosphere CGCM with improved coupling physics . J. Climate , 18 , 2344–2360 , doi: 10.1175/JCLI3404.1 . Manzini , E. , M. A. Giorgetta , M. Esch , L. Kornblueh , and E. Roeckner , 2006 : The influence of sea

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Shuguang Wang, Edwin P. Gerber, and Lorenzo M. Polvani

, found that BDC strengthens in response to tropical warming. Here we extend and reconcile these results by building upon the model of Gerber and Polvani (2009) , a dry primitive equation model on the sphere designed to capture stratosphere–troposphere coupling. We prescribe a tropical heating as in Butler et al. (2010) to mimic climate change, but its strength is systematically varied over a wide range. This procedure reveals an abrupt transition when the tropical warming exceeds a certain

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