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Jun-Ichi Yano and Joseph J. Tribbia

1. Introduction The Madden–Julian oscillation (MJO) is an atmospheric enigma [ Hartmann and Hendon 2007 ; see Zhang (2005) for a review]. Initiated over the Indian Ocean exhibiting growth of convective activity, an enhanced oceanwide horizontal convergence in the lower troposphere, and an upper-troposphere divergence, this planetary-scale system propagates eastward with a speed of 3–6 m s −1 ( Madden and Julian 1972 ). Accelerating its propagation speed as it crosses the date line with

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Michael S. Pritchard and Christopher S. Bretherton

focuses on just the role of the rotational component of the moisture advection and 2) that it focuses on a version of the Superparameterized Community Atmosphere Model (SPCAM) that has a well-validated MJO signal and a realistic (real geography) basic state. The first point is inspired by a philosophical view that vorticity is one of the likely sources of memory available in the tropics to help explain the slowness of the MJO as an internal atmospheric disturbance. The second point aims to break

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

1. Introduction The Madden–Julian oscillation (MJO) is the leading intraseasonal (30–60 day) mode of atmospheric variability of the equatorial atmosphere [ Madden and Julian (1971) , reviewed in Waliser (2006) ]. It comprises alternating zonal wind anomalies in the lower and upper troposphere of the planetary zonal scale. Deep convection accompanies surface convergence and upper-level divergence, and suppressed convection accompanies surface divergence. The 30–60-day time scale of the MJO is

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

1. Introduction Ocean–atmosphere interaction is a key process in tropical weather and climate. The moisture flux from the ocean to atmosphere increases approximately exponentially with sea surface temperature (SST) through the Clausius–Clapeyron and bulk flux relationships ( Fairall et al. 1996b ). These processes are core to the evolution of El Niño–Southern Oscillation (ENSO; Neelin et al. 1998 ) on interannual time scales. On shorter, intraseasonal time scales, ocean–atmosphere interaction

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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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Sharon L. Sessions, Stipo Sentić, and David J. Raymond

important as long as the scale of the convective disturbance exceeds the Rossby radius. According to Ooyama, tropical disturbances greater than O (1000) km, such as those observed during DYNAMO, are candidates by this criterion. Raymond et al. (2015) recast this in terms of time scales; if disturbances occur on time scales longer than those needed for the atmosphere to achieve balance, they evolve in response to balanced circulations. This criterion was also an explicit requirement in the derivation

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Tim Li, Chongbo Zhao, Pang-chi Hsu, and Tomoe Nasuno

radiation (OLR), confirmed the planetary scale of the MJO ( Weickmann 1983 ; Murakami and Nakazawa 1985 ; Lau and Chan 1986 ; Li and Zhou 2009 ). Studies also show that the oscillation is more broadband than the original 40–50-day period identified by Madden and Julian (1971) and can span a range of 20–100 days (e.g., Krishnamurti and Subrahmanyam 1982 ; Annamalai and Slingo 2001 ; Lau and Waliser 2005 ; Zhang 2005 ; Li and Wang 2005 , Waliser 2006 ). As the most significant variability

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

1. Introduction Since Madden and Julian (1972) found the eastward-propagating oscillations over the tropical Indo-Pacific region, many observational analyses have revealed a slowly eastward-propagating convective envelope characterized by planetary-scale circulation with a broad life span of 30–60 days (e.g., Lau and Chan 1986 ; Hendon and Salby 1994 ; Zhang 2005 ; Lau and Waliser 2005 ). Despite numerous studies about the Madden–Julian oscillation (MJO), some fundamental questions still

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Samson M. Hagos, Zhe Feng, Casey D. Burleyson, Chun Zhao, Matus N. Martini, and Larry K. Berg

surface rainfall as well as observed top-of-atmosphere and surface radiation based on the method developed by Zhang et al. (2001) . Three versions of the forcing data using the above-mentioned precipitation products are used to account for uncertainties in the rainfall estimates. The forcing dataset is used as a proxy for observations in this study rather than to drive model simulations (as they are commonly used). The length of the forcing time series is 90 days (1 October–31 December 2011). The

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