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Gui-Ying Yang, Julia Slingo, and Brian Hoskins

present there is little understanding of how well they are treated in state-of-the-art models and our overall knowledge of these waves is very limited. Current large-scale models fail to simulate well-organized tropical phenomena in which convection interacts with dynamics and physics. Lin et al. (2006) showed that 14 atmospheric global circulation models (AGCMs) that participated in the Intergovernmental Panel on Climate Change (IPCC) have significant problems in simulating tropical subseasonal

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Masaru Yamamoto and Masaaki Takahashi

the lower-atmospheric angular momentum. In other words, the fully developed superrotation is maintained by the meridional circulation and the eddies. The horizontal and vertical angular momentum fluxes of thermally induced waves produce the cloud-top equatorial superrotation of more than 100 m s −1 near the height region where the solar heating is strongest, and planetary-scale waves with phase velocities of 0–50 m s −1 transport angular momentum toward the equator in the lower atmosphere (<40

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Lisa S. Darby and Gregory S. Poulos

Springs region, the Federal Aviation Administration (FAA), in collaboration with the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research (NCAR), sponsored the Mountain-induced Clear Air Turbulence (MCAT) field experiment in the winter and spring of 1997 ( Bedard and Neilley 1998 ). A number of lee-wave events were sampled by a NOAA Doppler lidar during MCAT. This paper describes a single case on 1 April 1997, with an emphasis on the 0000–1200 UTC

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Jadwiga H. Richter, Fabrizio Sassi, and Rolando R. Garcia

or become unstable. This process occurs on very small scales and is not understood thoroughly [see the review by Fritts and Alexander (2003) and references therein]. The mean flow acceleration due to gravity waves increases with altitude due to the decreasing atmospheric density; as a result, in the mesosphere gravity waves are the dominant term in the global momentum budget. Gravity wave breaking also causes turbulence and mixes chemical constituents. Gravity wave parameterizations are very

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Joseph Allan Andersen and Zhiming Kuang

sharpened our view on wave-CISK. REFERENCES Arakawa , A. , and W. H. Schubert , 1974 : Interaction of a cumulus cloud ensemble with the large-scale environment. Part I. J. Atmos. Sci. , 31 , 674 – 701 . Arkin , P. A. , and P. E. Andanuy , 1989 : Estimating climatic-scale precipitation from space: A review. J. Climate , 2 , 1229 – 1238 . Bretherton , C. S. , 2003 : Wave-CISK. Encyclopedia of Atmospheric Sciences, J. R. Holton, J. A. Pyle, and J. Curry, Eds., Elsevier, 1019

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Takenari Kinoshita, Kaoru Sato, Kentaro Ishijima, Masayuki Takigawa, and Yousuke Yamashita

1. Introduction The transformed Eulerian mean (TEM) equation derived by Andrews and McIntyre (1976 , 1978 ) can be used to diagnose relations between wave activities and zonal-mean flow. The traditional residual mean flow is expressed as the sum of the Eulerian mean flow and quasi-Stokes correction under the assumptions of small amplitude and is written as follows: where and are the respective meridional and vertical ageostrophic flows, υ is the meridional geostrophic flow, θ is the

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Vivien Matthias and Marlene Kretschmer

generally supportive of this statement. While strongest and most persistent fluxes were found before and during event 2 (i.e., before the SSW), the first event was linked to a short period of enhances wave activity ( Fig. 3b ). Nevertheless, results for event 2 show that reflection can occur during the wave pulse leading to a SSW, indicating once more the individual characteristics of each major SSW ( Tripathi et al. 2015 ). Overall, it remains thus an important task to better understand the atmospheric

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Jeffrey Shaman, R. M. Samelson, and Eli Tziperman

1. Introduction Ray tracing is often used to explore the propagation of Rossby waves with stationary or near-stationary phase speeds. These ray trajectories indicate how information is communicated through the atmosphere over large distances, as well as the time scales over which this information is conveyed. Rossby wave ray tracing has provided insight into the atmospheric response to steady thermal and orographic forcing ( Hoskins and Karoly 1981 ), the response to low-frequency forcing ( Li

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Noboru Nakamura and Abraham Solomon

. Atmos. Sci. , 33 , 2285 – 2291 . Brunet , G. , and P. H. Haynes , 1996 : Low-latitude reflection of Rossby wave trains. J. Atmos. Sci. , 53 , 482 – 496 . Butchart , N. , and E. E. Remsberg , 1986 : The area of the stratospheric polar vortex as a diagnostic for tracer transport on an isentropic surface. J. Atmos. Sci. , 43 , 1319 – 1339 . Cai , M. , and R. C. Ren , 2007 : Meridional and downward propagation of atmospheric circulation anomalies. Part I: Northern Hemisphere

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Carlos F. M. Raupp and Pedro L. Silva Dias

1. Introduction The atmospheric flow is characterized by the existence of low-frequency fluctuations with time scales ranging from 20 to around 100 days ( Madden and Julian 1972 , 1994 ; Hayashi and Golder 1993 ; Ghil and Mo 1991 ). The dominant component of this intraseasonal variability of the atmospheric circulation in the tropics is the 40–50-day Madden–Julian oscillation (MJO), which is characterized in the troposphere by a planetary-scale (wavenumber 1–2) wave envelope having an

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