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Wanying Kang and Eli Tziperman

, including midlatitude blocking systems ( Martius et al. 2009 ; Bancalá et al. 2012 ), tropospheric quasi-stationary waves ( Cohen and Jones 2011 ), and strong polar vortex events ( Limpasuvan et al. 2004 ). SSW events are also observed to be related to tropical variability, including the quasi-biennial oscillation (QBO; Holton and Tan 1980 ) and the Madden–Julian oscillation (MJO; Garfinkel et al. 2014 , 2012 ; Kang and Tziperman 2017 , hereafter KT17 ). Specifically, KT17 showed that an

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Daisuke Takasuka and Masaki Satoh

1. Introduction Madden and Julian (1972) first presented a canonical view of tropical intraseasonal convection coupled with a planetary-scale zonal overturning circulation, which is now called the Madden–Julian oscillation (MJO). The MJO is typically characterized by large-scale convective envelopes organized in the equatorial Indian Ocean (IO), which subsequently propagate eastward slowly into the western Pacific (WP) and dissipate around the date line. The candidate mechanics underlying this

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Aneesh C. Subramanian, Markus Jochum, Arthur J. Miller, Raghu Murtugudde, Richard B. Neale, and Duane E. Waliser

1. Introduction Four decades have passed since Madden and Julian made the pioneering discovery of a 40–50-day oscillation in the zonal winds in the tropics ( Madden and Julian 1971 , 1972 ). This discovery has led to numerous studies of a phenomenon now aptly called the Madden–Julian oscillation (MJO). Although MJO dynamics are still not fully understood ( Madden and Julian 1994 ; Zhang 2005 ), MJO is known to interact with a panoply of climate phenomena across different spatial and temporal

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Katherine Thayer-Calder and David A. Randall

1. Introduction The Madden–Julian oscillation (MJO), an intraseasonal oscillation of convection and winds in the tropical Indian and western Pacific Oceans, is a very large, generally equatorial, eastward-propagating region of active convection, followed and/or preceded by an equally large eastward-moving region of clearer skies and suppressed convection ( Madden and Julian 1972 , 1994 ). The MJO spans 50 to 100 degrees longitude, or zonal wavenumbers 1 to 5, and its speed generally varies

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Bin Wang, Sun-Seon Lee, Duane E. Waliser, Chidong Zhang, Adam Sobel, Eric Maloney, Tim Li, Xianan Jiang, and Kyung-Ja Ha

1. Introduction Tropical atmospheric motion exhibits a significant energy peak on a broad range of 2–10 weeks, which is often referred to as tropical intraseasonal variability. The Madden–Julian oscillation (MJO) is the dominant mode of tropical intraseasonal variability that bridges weather and climate variations ( Zhang 2013 ) and is a major source of global predictability on the subseasonal time scale ( Waliser et al. 2012 ). Notable progress has been made in steadily improving MJO

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James J. Benedict and David A. Randall

1. Introduction The Madden–Julian oscillation (MJO), an eastward-moving couplet of convectively active and suppressed atmospheric conditions in the Indian and west Pacific Ocean regions, is the leading mode of tropical variability on 30–60-day (intraseasonal) time scales. Since its discovery in the early 1970s ( Madden and Julian 1971 ), a host of observational, theoretical, and modeling studies have gradually improved our understanding of the MJO but have also revealed its many complexities (e

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Elinor R. Martin and Courtney Schumacher

intraseasonal variability in the Pacific, the Madden–Julian oscillation ( Madden and Julian 1971 ), and Gulf of Mexico hurricane numbers was identified by Maloney and Hartmann (2000b) . In addition, Barlow and Salstein (2006) showed a relationship between the MJO and summertime precipitation in Mexico and Central America. The MJO is suggested to affect Central America and modulate hurricane activity in the Gulf of Mexico through the generation of a Kelvin wave by the main region of MJO convection in the

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Fei Liu and Bin Wang

1. Introduction The Madden–Julian oscillation (MJO), named after its discoverers ( Madden and Julian 1971 ), features an equatorially trapped, slowly eastward-propagating (about 5 m s −1 ), planetary-scale baroclinic circulation cell in the Eastern Hemisphere ( Knutson and Weickmann 1987 ; Wang and Rui 1990a ; Hendon and Salby 1994 ; Maloney and Hartmann 1998 ; Kiladis et al. 2005 ; Zhang 2005 ). The MJO circulation comprises equatorial Kelvin waves and Rossby waves and exhibits a

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Stephanie A. Henderson, Eric D. Maloney, and Elizabeth A. Barnes

Southern Hemisphere, Australian blocking and rainfall was found to be influenced by ENSO heating and by intraseasonal convection anomalies near Indonesia ( Pook et al. 2013 ; Marshall et al. 2014 ). On intraseasonal time scales, tropical heating variability associated with the Madden–Julian oscillation (MJO) has been demonstrated to significantly perturb the midlatitude flow, with consequences for blocking including changes in Pacific wave breaking ( Moore et al. 2010 ) and the North Atlantic

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Eriko Nishimoto and Shigeo Yoden

convection over the western and eastern Pacific when the zonal-mean zonal wind in the lower stratosphere is easterly phase of the QBO (E-QBO phase), compared with those when it is westerly phase of the QBO (W-QBO phase). Kuma (1990) performed spectral analysis using the zonal wind data observed by the radiosonde at Singapore and showed that the intensity of the intraseasonal oscillation at 150 hPa is well correlated with the stratospheric QBO. Liu et al. (2014) showed that amplitude of the Madden–Julian

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