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Piet Termonia

1. Introduction Initial states of atmospheric models are usually unbalanced. When used as initial states of model runs, they will adjust to equilibrium by producing unrealistically high gravity–inertia waves. Initialization is the technique that creates balanced states by removing these waves. The technique of digital-filtering initialization (DFI) introduced by Lynch (1990) is based on the fact that the gravity–inertia waves lie in a different part of the frequency spectrum than the

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J. V. Ratnam, S. K. Behera, Y. Masumoto, and T. Yamagata

precipitation variations at the western Pacific are known to generate teleconnections (Pacific–Japan teleconnection; Nitta 1987 ) modulating the precipitation over Japan. The Pacific–Japan teleconnection is an atmospheric Rossby wave response to the heating over the western Pacific extending from the Philippine Sea to the extratropical North Pacific. Nitta (1987) found that, during the years of warm SST anomalies over the western Pacific, the intense convective regions are shifted to the south of

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Stephanie Leroux, Nicholas M. J. Hall, and George N. Kiladis

1. Introduction On synoptic scales, African easterly waves (AEWs) are the dominant mode of atmospheric variability over West Africa in summer (June–September). AEWs are baroclinic westward-propagating disturbances observed in convective and dynamical fields, with wavelengths of about 3000–6000 km and periods of 3–5 days [see Kiladis et al. (2006) for a recent composite study]. They appear as intermittent wave packets on intraseasonal time scales. A large range of studies have already

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Guanghua Chen and Chi-Yung Tam

wavelike pattern can be identified on that day. Meanwhile, Typhoons Rammasum and Chataan formed in the cyclonic regions of the wave train. During the subsequent several days, the low-level atmosphere near the equator started to exhibit wavelike characters with eastward expansion along the equator. In particular, the maximum meridional wind occurred at the equator but without closed circulations. On 5 July, the equatorial atmospheric response was enhanced, leading to the closed cyclonic and anticyclonic

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Hai Lin, Gilbert Brunet, and Jacques Derome

1. Introduction The Madden–Julian oscillation (MJO) is the dominant mode of intraseasonal variability in the Tropics. It organizes convection and precipitation, thus has a great impact on the weather in the Tropics. It has a significant influence on the extratropical atmospheric variability, possibly through Rossby wave propagation (e.g., Ferranti et al. 1990 ; Hsu 1996 ), and thus could provide an important signal source for the extratropical weather forecasts on intraseasonal time scales

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M. L. R. Liberato, J. M. Castanheira, L. de la Torre, C. C. DaCamara, and L. Gimeno

point of view of the energy associated with the forcing waves. The main goal of this work is therefore to perform a diagnostic study of the total (i.e., kinetic + available potential) energy associated with the planetary waves that force the vortex dynamics. The analysis is based on a three-dimensional (3D) normal mode decomposition of the atmospheric global circulation, which is partitioned into planetary Rossby waves and inertio–gravity waves, both types of waves possessing barotropic and

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Adam R. Edson and Peter R. Bannon

]. Atmospheric applications include the momentum forcing due to gravity waves that is an important component of the general circulation of the middle atmosphere (e.g., Fritts 1993 ). The sources of the gravity waves include excitation by airflow over orography, tropospheric convective activity, and jet stream adjustment. Various mechanisms (e.g., critical layer absorption and wave breaking) lead to the deposition of the gravity wave momentum. Zhu and Holton (1987) describe the atmospheric response to such

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Enver Ramirez, Pedro L. da Silva Dias, and Carlos F. M. Raupp

to develop simplified multiscale atmospheric models for scale interactions can be noted (e.g., Majda and Klein 2003 ; Majda and Biello 2003 ; Biello and Majda 2005 ; Raupp and Silva Dias 2005 , 2006 , 2009 , 2010 ). The scale interactions can be responsible for the connection between weather and climate responses and involve either upscale or downscale cascade fluxes ( Torrence and Webster 1999 ; Biello and Majda 2005 ) or discrete wave interactions ( Raupp et al. 2008 ; Raupp and Silva

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Kathleen D. Holman, David J. Lorenz, and Michael Notaro

of changes in the mean vorticity and divergence fields between the two months. Their results emphasize the importance of monthly, rather than seasonal, analyses in exploring and understanding Rossby wave propagation. In this paper, we expand on previous research by exploring the direct relationship between precipitation in the Great Lakes region and large-scale atmospheric circulation patterns, namely, atmospheric Rossby waves. Using reanalysis data, we explore how variability in the upper

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A. J. Bedard Jr., F. Canavero, and F. Einaudi

2838 JOURNAL OF THE ATMOSPHERIC SCIENCES .VOL 43, NO. 23Atmospheric Gravity Waves and Aircraft Turbulence Encounters A. $. BEDARD, JR.Wave Propagation Laboratory, National Oceanic and Atmospheric Adrninistration, Boulder, CO 80303 F. CANAVERODipartirnento di E!ettronica, Politecnico di Torino, 10129 Turin, Italy F. EINAUDISchool of Geophysical Sciences, Georgia Institute of

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