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H. Bellenger, R. Wilson, J. L. Davison, J. P. Duvel, W. Xu, F. Lott, and M. Katsumata

developed by W10 to properly treat the instrumental-noise issue. Turbulence can originate from static instabilities or from Kelvin–Helmholtz instabilities. These instabilities can be associated with gravity wave (GW) activity ( Cadet 1977 ; Barat 1983 ; Chao and Schoeberl 1984 ; Fritts and Dunkerton 1985 ; Fritts and Rastogi 1985 ; Fritts et al. 1988b ; Pavelin et al. 2001 ; Sharman et al. 2012 ; Fritts et al. 2016 ). This suggests the possibility of GWs playing a role in the formation of the

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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

made in understanding and forecasting the MJO over the past four decades, it remains a significant outstanding problem in tropical meteorology (see Zhang et al. 2013 ). As discussed in detail by Straub (2013 , hereafter S13 ), one of the challenges faced by researchers studying the MJO has to do not only with tracking the disturbance through time, but simply defining it. This difficulty stems from the fact that the MJO is associated with strong planetary circulation anomalies, and similar

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Wen-wen Tung, Dimitrios Giannakis, and Andrew J. Majda

1. Introduction The Madden–Julian oscillation (MJO; e.g., Madden and Julian 1971 , 1972 ) is an eastward-propagating, planetary-scale envelope of organized convective activity in the tropics. Characterized by gross features in the 20–90-day intraseasonal time range and zonal wavenumbers 1–4, it dominates tropical variability in subseasonal time scales. Moreover, through tropical–extratropical interactions, it influences global weather and climate variability, fundamentally linking short

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Simon P. de Szoeke

2009 ; Chikira 2014 ) emphasize feedbacks to tropospheric moisture for creating unstable intraseasonal convective modes in the column MSE budget. The tropical intraseasonal skeleton model of Majda and Stechmann (2009) suggests that BL moisture east of the area of active MJO convection stimulates synoptic wave activity that supports the spatial structure of the MJO. The ( Wang et al. 2016 ) trio-interaction theory for the MJO explores interactions among convection, moisture, and BL wave dynamics

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Eric D. Skyllingstad and Simon P. de Szoeke

1. Introduction Within 10° latitude of the equator, organized atmospheric convection occurs across scales ranging from individual thunderstorm systems to planetary-scale disturbances such as the Madden–Julian oscillation (MJO). Understanding what drives these different scales is a key question for tropical weather prediction and accurate simulation of the atmospheric general circulation. At the cloud scale, we have a fairly good knowledge of convective system structure and the processes that

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Simon P. de Szoeke and Eric D. Maloney

planetary-scale intraseasonal convective anomalies. Among many possible positive feedbacks, surface fluxes have been proposed to destabilize the atmosphere to the MJO ( Krishnamurti et al. 1988 ; Maloney and Sobel 2004 ). An early theory for the MJO proposed wind-induced surface heat exchange as important for MJO destabilization and propagation ( Emanuel 1987 ; Neelin et al. 1987 ). Forcing an atmospheric model with fluxes due to strong SST anomalies enhances its intraseasonal convection (e

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Matthew A. Janiga and Chidong Zhang

1. Introduction The Madden–Julian oscillation (MJO) is a planetary-scale phenomenon that modulates convective activity in the tropics on intraseasonal time scales (30–100 days) ( Madden and Julian 1971 , 1972 ). The MJO is characterized by an envelope of increased rainfall and free-tropospheric water vapor that originates over the Indian Ocean, propagates eastward at 5–8 m s −1 , and dissipates over the central Pacific. This convective envelope modulates rainfall and tropical cyclogenesis as

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Douglas C. Stolz, Steven A. Rutledge, Weixin Xu, and Jeffrey R. Pierce

, S. S. Babu , R. R. Reddy , and K. R. Gopal , 2009 : Large scale modulations of spectral aerosol optical depths by atmospheric planetary waves . Geophys. Res. Lett. , 36 , L03810 , doi: 10.1029/2008GL036509 . 10.1029/2008GL036509 Boccippio , D. J. , S. J. Goodman , and S. Heckman , 2000 : Regional differences in tropical lightning distributions . J. Appl. Meteor. , 39 , 2231 – 2248 , doi: 10.1175/1520-0450(2001)040<2231:RDITLD>2.0.CO;2 . 10

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Adrian J. Matthews, Dariusz B. Baranowski, Karen J. Heywood, Piotr J. Flatau, and Sunke Schmidtko

diurnal warm layer and the state of the MJO is certainly not a perfect one. Convection and related conditions at a single geographical point (the glider location) are subject to large variability, as the planetary-scale MJO envelope is made up of contributions from multiple scales. This can clearly be seen in the time series of precipitation, wind speed, and shortwave radiation at the glider location ( Fig. 2b ). The tendency for wet, windy, and cloudy conditions in the active MJO stage and for dry

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Richard H. Johnson and Paul E. Ciesielski

boundary layer modification by convective clouds and precipitation. The challenge extends well beyond individual clouds to organized convective systems across a wide span of time scales, from mesoscale convective systems to equatorial waves to the Madden–Julian oscillation (MJO). The recent Dynamics of the MJO (DYNAMO) 1 field campaign ( Yoneyama et al. 2013 ; Zhang et al. 2013 ) affords a unique opportunity to investigate the multiscale variability of the boundary layer under a wide range of

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