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K-M. Lau and H-T. Wu

1. Introduction The Madden–Julian oscillation (MJO; Madden and Julian 1972 ) is a dominant feature in the tropical ocean–atmosphere, linking weather and climate variability. Theories and observational characteristics of MJO and its influence on tropical cyclones, midlatitude weather, monsoon variability, air–sea interaction, relationships with atmospheric angular momentum and El Niño, and predictability have been reported in a large number of previous studies. [See Lau and Waliser (2005) for

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Xianan Jiang, Duane E. Waliser, William S. Olson, Wei-Kuo Tao, Tristan S. L’Ecuyer, Jui-Lin Li, Baijun Tian, Yuk L. Yung, Adrian M. Tompkins, Stephen E. Lang, and Mircea Grecu

1. Introduction The Madden–Julian oscillation (MJO; Madden and Julian 1994 ) is the most important form of tropical subseasonal variability and its significant role in our weather and climate systems has been widely recognized (e.g., Lau and Waliser 2005 ; Zhang 2005 ). The MJO has been intimately associated with active/break modulation of the global monsoon systems (e.g., Lau and Chan 1986 ; Hendon and Liebmann 1990 ) and tropical cyclone genesis (e.g., Maloney and Hartmann 2000 ; Mo

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Shaocheng Xie, Timothy Hume, Christian Jakob, Stephen A. Klein, Renata B. McCoy, and Minghua Zhang

island-initiated convective systems over the Darwin region were studied in Carbone et al. (2000) and were the major focus of the Maritime Continent Thunderstorm Experiment (MCTEX) held during November–December 1995 over the Tiwi Islands north of Darwin ( Keenan et al. 2000 ). During TWP-ICE, Darwin experienced four distinct synoptic regimes, coincident with the activity of a major Madden–Julian oscillation (MJO) event that influenced the region (see the MJO index online at http

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Manuel D. Zuluaga, Carlos D. Hoyos, and Peter J. Webster

principal source region of monsoon intraseasonal variability (e.g., Webster et al. 1998 ; Lawrence and Webster 2002 ; Wang et al. 2005 , 2006 ). This variability generates active and break periods over Southeast Asia on a 25–80-day time scale and is referred to as the monsoon intraseasonal oscillation (MISO), or the summer manifestation of the Madden–Julian oscillation (MJO; Zhang 2005 ). In general, the MISO develops first in the western equatorial Indian Ocean, propagates eastward along the

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Richard H. Johnson, Paul E. Ciesielski, Tristan S. L’Ecuyer, and Andrew J. Newman

and Yasunari (2006) , the diurnal cycle impacts processes on the intraseasonal time scale, thereby complicating the treatment of the Madden–Julian oscillation (MJO; Madden and Julian 1971 ). The diurnal cycle of rainfall is particularly prominent in coastal and mountainous areas of the monsoon regions and Indonesian Maritime Continent ( Janowiak et al. 2005 ). While observations of the diurnal cycle of convection have increased dramatically during the past decade, clarification of the mechanisms

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T. N. Krishnamurti, Arindam Chakraborty, and A. K. Mishra

. Krishnamurti , 2003 : Improvement of the multimodel superensemble technique for seasonal forecasts. J. Climate , 16 , 3834 – 3840 . Yuter , S. , J. R. A. Houze , E. Smith , T. Wilheit , and E. Zipser , 2005 : Physical characterization of tropical oceanic convection observed in KWAJEX. J. Appl. Meteor. , 44 , 385 – 415 . Zhang , C. , 2005 : Madden-Julian Oscillation. Rev. Geophys. , 43 , RG2003 . doi:10.1029/2004RG000158 . Zhang , C. , M. Dong , H. H. Hendon , E. D

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Yukari N. Takayabu, Shoichi Shige, Wei-Kuo Tao, and Nagio Hirota

systems, two peaks in the cloud-top distribution at ∼6 and ∼2 km are significant. The trimodal structure is also observed in association with a three-step-wise development of large-scale cloud systems such as the Madden–Julian oscillation (MJO) over the western Pacific ( Kikuchi and Takayabu 2004 ). The importance of a substantial amount of shallow heating is emphasized by Zhang et al. (2004) , who found a low-level meridional return flow associated with the shallow heating in the eastern Pacific

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Mircea Grecu, William S. Olson, Chung-Lin Shie, Tristan S. L’Ecuyer, and Wei-Kuo Tao

Johnson and Ciesielski 2002 ). More recently, estimates of Q 1 and Q 2 were derived from rawinsonde network data collected during the Mirai Indian Ocean cruise for the Study of the Madden–Julian Oscillation Convection Onset (MISMO; October–December 2006). Surface rain rates were estimated as a residual of the moisture budget in a manner similar to Johnson and Ciesielski (2002) , using additional shipboard flux measurements. MISMO estimates of surface rain rate and Q 1 were provided by Dr

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Tristan S. L’Ecuyer and Greg McGarragh

heating rate profiles are largest (relative to other time scales) in the TWP and Congo, suggesting that some level of convective organization exists on multiday time scales. These time scales of variability are loosely consistent with the propagation of the Madden–Julian oscillation (MJO) across the 30° TWP region and African easterly waves (AEWs) in the Congo ( Wheeler and Kiladis 1999 ; Nguyen and Duvel 2008 ). The lack of a significant increase in heating rate variability in the Amazon, on the

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