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  • Waves, oceanic x
  • DYNAMO/CINDY/AMIE/LASP: Processes, Dynamics, and Prediction of MJO Initiation x
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H. Bellenger, R. Wilson, J. L. Davison, J. P. Duvel, W. Xu, F. Lott, and M. Katsumata

-wavelength/higher-frequency waves are likely to be observed close to their source, whereas longer-wavelength/lower-frequency GWs can propagate great distance away from their sources (e.g., Hankinson et al. 2014a , b ). Over the central equatorial Indian Ocean, which lacks any significant orography, the most probable GW sources are convection and jet streams. Therefore, we anticipate an observable link between convective activity (both local and distant), GW characteristics, and turbulence. This study is based on radiosonde

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Sue Chen, Maria Flatau, Tommy G. Jensen, Toshiaki Shinoda, Jerome Schmidt, Paul May, James Cummings, Ming Liu, Paul E. Ciesielski, Christopher W. Fairall, Ren-Chieh Lien, Dariusz B. Baranowski, Nan-Hsun Chi, Simon de Szoeke, and James Edson

the time scale for the observed moisture resurgence in the post-MJO dry air mass prior to the subsequent MJO onset? What relative roles do diurnal ocean temperature anomalies and surface fluxes play in regulating or initiating the deep vapor resurgence? Do transient Kelvin, Rossby, mixed Rossby–gravity, and inertio-gravity waves impact the vapor resurgence? We begin with a description of the data and modeling methods used in section 2 . Analyses of observed in situ rawindsondes, surface flux, and

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James N. Moum, Simon P. de Szoeke, William D. Smyth, James B. Edson, H. Langley DeWitt, Aurélie J. Moulin, Elizabeth J. Thompson, Christopher J. Zappa, Steven A. Rutledge, Richard H. Johnson, and Christopher W. Fairall

. (a) Hovmöller plot of TRMM precipitation at the equator and across the Indian Ocean for the period of MJO2 (blue image color); corresponding contours of OLR = 200 W m −2 (black). Green lines indicate propagating disturbances in TRMM at roughly the atmospheric Kelvin wave speed, 8.6 m s −1 . Note that the OLR signal travels more slowly than the rain signal. (b) Time series of precipitation from TRMM (blue shading; averaged ±0.5° both zonally and meridionally about the ship position at 0°, 80.5°E

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Yue Ying and Fuqing Zhang

precipitation over the Indian Ocean (50°–90°E) is organized into several 2-day episodes that are modulated by the phase of the MJO and several episodes of westward-propagating equatorial Rossby waves and eastward-propagating equatorial Kelvin waves (hereafter referred to as Rossby and Kelvin waves for simplicity). The model simulation of these finer-scale features is less accurate than the MJO signal itself as compared to the observations. There are generally mismatches in timing of the IG waves over the

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Tomoe Nasuno, Tim Li, and Kazuyoshi Kikuchi

description of how it led to convective initiation (e.g., in terms of moisture buildup) was presented. Moreover, extratropical forcing sometimes emerges as specific weather events, such as an outbreak of cold surges ( Wang et al. 2012 ) or in an enhancement of Rossby wave activity ( Hsu et al. 1990 ). Accumulation of case studies is indispensable when tackling the MJO initiation problem. The Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011)/Dynamics of the

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

1. Introduction The Madden–Julian oscillation (MJO) is a dominant mode of tropical convection variability on intraseasonal time scales ( Madden and Julian 1971 ; Zhang 2005 ; Lau and Waliser 2011 ). The MJO convective envelope usually initiates over equatorial Africa and the western equatorial Indian Ocean ( Wang and Rui 1990a ). The associated circulation systems propagate eastward as a Kelvin–Rossby wave couplet ( Wang 1988a ; Wang and Rui 1990b ; Hendon and Salby 1994 ; Roundy 2012

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Ji-Hyun Oh, Xianan Jiang, Duane E. Waliser, Mitchell W. Moncrieff, Richard H. Johnson, and Paul Ciesielski

. E. , and Coauthors , 2014 : Quality-controlled upper-air sounding dataset for DYNAMO/CINDY/AMIE: Development and corrections . J. Atmos. Oceanic Technol. , 31 , 741 – 764 , doi: 10.1175/JTECH-D-13-00165.1 . DePasquale , A. , C. Schumacher , and A. Rapp , 2014 : Radar observations of MJO and Kelvin wave interactions during DYNAMO/CINDY2011/AMIE . J. Geophys. Res. Atmos. , 119 , 6347 – 6367 , doi: 10.1002/2013JD021031 . Fu , X. , J.-Y. Lee , P.-C. Hsu , H. Taniguchi

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Brandon W. Kerns and Shuyi S. Chen

( Hoell et al. 2012 ), heat waves, and tropical cyclones ( Molinari and Vollaro 2000 ; Maloney and Hartmann 2001 ). The influence of the MJO varies regionally. Rainfall and low-level winds are most affected in regions where deep convection is climatologically favored: the Indian Ocean (IO), Maritime Continent, and western Pacific Ocean. The convection tends to persist longest in the IO and western Pacific (WPAC). The eastward progression of the MJO resembles a “seesaw” between the IO and WPAC ( Zhu

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Simon P. de Szoeke, James B. Edson, June R. Marion, Christopher W. Fairall, and Ludovic Bariteau

surface is enhanced under stronger wind speeds to the east of the maximum upward velocity anomaly for easterly mean winds. Contrary to the eastward propagation of the MJO, the original WISHE theory predicts westward propagation of disturbances for the mean westerlies found over the Indian Ocean and western Pacific. Under weak planetary rotation (implying large Rossby radius of deformation) gravity waves efficiently redistribute temperature anomalies throughout the tropics. The resulting relatively

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Kai-Chih Tseng, Chung-Hsiung Sui, and Tim Li

’s circulation weakens but reintensifies upon reaching the Pacific warm pool. Actually, many MJOs evolve differently from this typical life cycle: some behave more like a stationary dipole oscillation over the Indian Ocean and the warm pool. The previous theories explaining the propagating mechanism can be separated into two sets of theories: the tropical wave dynamics and the moisture mode. In the set of wave dynamics, the eastward propagation of MJOs is first explained by Kelvin waves based on the forced

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