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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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Paul E. Ciesielski and Richard H. Johnson

formed in this period over the Indian Ocean originated from wake vortices shed downstream of significant topographic features in the “Maritime Continent.” A second significant impact islands have on their circulation is the generation of convection due to the convergence of coastal sea and land breezes with the ambient flow. Mori et al. (2004) demonstrated how such convergence leads to an eastward-migrating peak in rainfall over Sumatra Island during the day and a westward-migrating offshore peak

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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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James H. Ruppert Jr. and Fuqing Zhang

pronounced variability at higher frequencies in addition to the intraseasonal evolution. A prominent component of that over the Indian Ocean is due to 2-day waves ( Zuluaga and Houze 2013 ; Yu et al. 2018 ). Two-day waves have been noted across the Indo-Pacific warm pool region and extensively studied, although their exact cause remains uncertain ( Chen and Houze 1997 ; Takayabu et al. 1996 ; Haertel and Kiladis 2004 ). Yet the most prominent, regular, and coherent signal at high frequency is that due

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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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Angela K. Rowe, Robert A. Houze Jr, Stacy Brodzik, and Manuel D. Zuluaga

tropical ocean shades the ocean and prevents the surface air temperature from recovering for a day after a deep convective episode. The result is a bidiurnal cycle of deep convection at a specific location. Sometimes this bidiurnal cycle can become sympathetic with a 2-day propagating wave. Yu et al. (2018) found evidence that 2-day rainfall variability was associated with the relationship between the diurnal cycle and quasi-2-day westward-propagating disturbances during the October MJO event in

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