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CLIVAR MADDEN–JULIAN OSCILLATION WORKING GROUP:

1. Introduction The Madden–Julian oscillation ( Madden and Julian 1971 , 2005 ) is the dominant component of intraseasonal variability in the tropical atmosphere. It is characterized by eastward-propagating, equatorially trapped, baroclinic oscillations in the tropical wind field. During a typical MJO event, a positive convection/rainfall anomaly develops over the western Indian Ocean, while convection tends to be suppressed further east over the western Pacific. Over the course of 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 , 1972 , 1994 ), 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 1990 ; 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

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Liping Deng, Sally A. McFarlane, and Julia E. Flaherty

1. Introduction The Madden–Julian oscillation (MJO) ( Madden and Julian 1972 , 1994 ) is a dominant mode of intraseasonal (30–90 days) variability in the tropical atmosphere. Its characteristics and structure have been well documented by previous studies (e.g., Kiladis et al. 2005 ; Lau and Waliser 2005 ; Zhang 2005 ; Wu et al. 2007 ; Jiang et al. 2009 ; Zhang et al. 2010 ). The organization and evolution of tropical convection is a major component of the MJO and generally includes

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Klaus Weickmann and Edward Berry

) atmospheric dynamics and “external” boundary forcing (e.g., sea surface temperature) influence the evolution of the coupled ocean–atmosphere system. Understanding the time and space scales of the band, and its interaction with adjacent time bands, is a scientific challenge with applications to global weather–climate modeling and extended-range prediction. The tropical Madden–Julian oscillation (MJO; Madden and Julian 1972 ) and the extratropical teleconnection patterns ( Wallace and Gutzler 1981 ) are

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Fei Liu and Bin Wang

1. Introduction The Madden–Julian oscillation (MJO), as a significant driver of global circulation with a period of 30–90 days, is characterized by a zonal planetary scale and slow eastward propagation (5 m s −1 ) over the tropical Indian and western Pacific Oceans ( Zhang 2005 ). The MJO has different spectral characteristics from the moist Kelvin waves, since its frequency is nearly independent of wavelength, whereas the frequency of the moist Kelvin waves increases with wavenumber linearly

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Daehyun Kim, Jong-Seong Kug, and Adam H. Sobel

1. Introduction The Madden–Julian oscillation (MJO) is the dominant mode of intraseasonal variability in the tropics ( Madden and Julian 1972 ). A few distinct characteristics of the MJO are its vast horizontal scale (wavenumber 1–3), the time scale shorter than a season but longer than a month (30–60-day period), and the eastward propagation. The MJO interacts with many short-term weather and climate phenomena ( Takayabu et al. 1999 ; Maloney and Hartmann 2000 ; Wheeler and McBride 2005

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Traute Crueger, Bjorn Stevens, and Renate Brokopf

1. Introduction The Madden–Julian oscillation (MJO) is the dominant mode of intraseasonal variability in boreal winter and/or spring in the equatorial tropics. Discovered by Madden and Julian (1971 , 1972 , 1994 ), its salient features are coherent eastward propagating patterns of enhanced and suppressed convection over the Indian Ocean, the Indo-Pacific warm pool, and the western Pacific Ocean. Because it describes an envelope of convective activity, and hence precipitation, the MJO is

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Danyang Wang, Jun-Ichi Yano, and Yanluan Lin

1. Introduction The tropical atmospheric Madden–Julian oscillation (MJO) is an eastward-propagating wavelike entity associated with strong convective activity ( Zhang 2005 ). For this reason, the MJO is often considered an equatorial wave strongly coupled with convection (e.g., Emanuel 1987 ; Yano and Emanuel 1991 ; Fuchs and Raymond 2007 ; Raymond and Fuchs 2007 , 2009 ; Majda and Stechmann 2009 ). Recently, Yano and Tribbia (2017) proposed an alternative theory that explains the MJO

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Bin Guan, Duane E. Waliser, Noah P. Molotch, Eric J. Fetzer, and Paul J. Neiman

status may be possible if storm activities are considerably mediated by the slowly varying large-scale atmospheric/oceanic conditions, such as those related to the Madden–Julian oscillation (MJO). It is generally understood that the tropical/subtropical Pacific Ocean has far reaching impacts on the U.S. weather and climate. A number of studies have linked the MJO to changes in the North Pacific circulation patterns and West Coast precipitation ( Higgins and Mo 1997 ; Mo and Higgins 1998 ; Bond and

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Philip J. Klotzbach

1. Introduction The Madden–Julian oscillation (MJO) ( Madden and Julian 1972 ) is a large-scale mode of tropical variability that propagates around the globe on an approximately 30–60-day time scale. As it does so, it alters large-scale fields known to impact tropical cyclone (TC) activity, such as vertical wind shear, vertical motion, relative vorticity, and low- and midlevel moisture. Gray (1979) was one of the first to note that TCs tend to cluster in time, with active periods of one to

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