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Jian Ling, Peter Bauer, Peter Bechtold, Anton Beljaars, Richard Forbes, Frederic Vitart, Marcela Ulate, and Chidong Zhang

increase with increasing speed up beyond 12 m s −1 . Even if a track with maximum averaged precipitation can be found at a speed greater than 12 m s −1 , it cannot be considered as an MJO event. Therefore, no track is identified in the forecast for the December MJO event. d. Numerical experiments Three sets of numerical experiments were conducted: observational data denial, humidity relaxation, and SST forcing ( Table 3 ). The observational denial experiments were designed to explore the impact of

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Eric D. Skyllingstad and Simon P. de Szoeke

active phase of the MJO develops. Fig . 1. Skew T –log p temperature profile (solid) for the average DYNAMO conditions from the R/V Revelle along with a histogram of (a) observed temperature and (b) observed dewpoint temperature. The dashed line signifies the dewpoint temperature used in the model initial conditions. In this study we employ a cloud-resolving large-eddy simulation (LES) model to examine how convection responds to external forcing from prescribed domain-scale moisture convergence

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Xiouhua Fu, Wanqiu Wang, June-Yi Lee, Bin Wang, Kazuyoshi Kikuchi, Jingwei Xu, Juan Li, and Scott Weaver

external SST forcing on intra-seasonal time scales may enhance the atmospheric responses toward an eventual satisfactory simulation of intra-seasonal oscillation.” Two MJO events along with coherent upper-ocean variability were first documented by the TOGA COARE field campaign from November 1992 to February 1993 ( Yanai et al. 2000 ; Richards et al. 1995 ; Weller and Anderson 1996 ), although this program was geared to advance the understanding and prediction of El Niño–Southern Oscillation (ENSO

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Tomoe Nasuno, Tim Li, and Kazuyoshi Kikuchi

: those stressing tropical internal dynamics [e.g., a circumnavigating signal of the previous episode: Lau and Peng (1987) ; Wang and Li (1994) ; Kikuchi and Takayabu (2003) ; Matthews (2008) ; or local processes in the tropics: Hu and Randall (1994) ; Jiang and Li (2005) ; Straub (2013) ] and those emphasizing extratropical forcing (e.g., Hsu et al. 1990 ; Bladé and Hartmann 1993 ; Matthews and Kiladis 1999 ; Pan and Li 2007 ; Lin et al. 2007 ; Ray and Zhang 2010 ; Wang et al. 2012

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Jean-Philippe Duvel

this stage, however, it is difficult to consider the MJO modulation of the PV gradient as a pure forcing. The presence of more TDs in active phases may also influences the PV gradient and may explain part of the gradient reduction, especially for phases 5 and 6. Other aspects of the MJO influence are discussed below. As noted above, the strengthening of the meridional shear of the zonal wind results from a reinforcement of both westerlies to the north and easterlies to the south. Westerlies near

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Brandon W. Kerns and Shuyi S. Chen

’Ecuyer , 2004 : Observational evidence for the mutual regulation of the tropical hydrological cycle and tropical sea surface temperatures . J. Climate , 17 , 2213 – 2224 . Straub , K. H. , and G. N. Kiladis , 2003 : Extratropical forcing of convectively coupled Kelvin waves during austral winter . J. Atmos. Sci. , 60 , 526 – 543 . Takaya , K. , and H. Nakamura , 1997 : A formulation of a wave-activity flux for stationary Rossby waves on a zonally varying basic flow . Geophys. Res. Lett

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George N. Kiladis, Juliana Dias, Katherine H. Straub, Matthew C. Wheeler, Stefan N. Tulich, Kazuyoshi Kikuchi, Klaus M. Weickmann, and Michael J. Ventrice

13 , the fact that the RMM amplitude may at times be weak even with the presence of an “MJO like” convective signal, or strong in the absence of such a signal, raises the question of which fundamental characteristics of the MJO should be used to define it. While we will not directly address this issue here, we point out that the essential circulation features of MJO teleconnections in both the tropics and extratropics can be reproduced in a dry primitive equation model by forcing associated with

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