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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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Tristan S. L’Ecuyer and Greg McGarragh

1. Introduction Diabatic heating Q 1 plays a central role in driving atmospheric (ATM) variability on a wide range of time and space scales. The vertical structure of Q 1 has been shown to influence the atmosphere on scales ranging from the life cycle of individual mesoscale convective systems (e.g., Houze 1982 , 1989 ; Mapes and Houze 1995 ) and the evolution of extratropical cyclones ( Weaver 1999 ) to the propagation speed of tropical intraseasonal oscillations (e.g., Lau and Peng

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Yasu-Masa Kodama, Masaki Katsumata, Shuichi Mori, Sinsuke Satoh, Yuki Hirose, and Hiroaki Ueda

1. Introduction The global distribution of precipitation is related to water circulation in the climate system and to latent heating (LH) in the atmosphere, which is an important heat source driving atmospheric circulation ( Nigam et al. 2000 ). Characteristics of precipitation change greatly over a wide spectrum according to precipitation type and surface and atmospheric conditions. Satellite observations of clouds have provided useful but indirect information on precipitation. Precipitation

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Samson Hagos, Chidong Zhang, Wei-Kuo Tao, Steve Lang, Yukari N. Takayabu, Shoichi Shige, Masaki Katsumata, Bill Olson, and Tristan L’Ecuyer

1. Introduction To the first order, the atmospheric general circulation redistributes energy and balances the horizontal and vertical gradients of diabatic heating. Since the earth’s atmosphere is primarily heated from the surface, convective processes are required to maintain the troposphere close to neutral stratification. On the large scale, the heating gradient between the tropics and extratropics is balanced by the poleward transport of the heat of the general circulation. However, the

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Wei-Kuo Tao, Stephen Lang, Xiping Zeng, Shoichi Shige, and Yukari Takayabu

1. Introduction The release of latent heating (LH) during the formation of precipitation is of immense consequence to the nature of large- and small-scale atmospheric circulations, particularly in the tropics where various large-scale tropical modes controlled by LH persist and vary on a global scale. Latent heat release and its variations are without doubt the most important diabatic processes within the atmosphere, and thus play a central role in the earth’s water cycle. Latent heating is

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

1. Introduction Over the tropical and subtropical oceans, destabilization of the atmosphere by warm sea surface temperatures (SSTs) and the stabilization by subsidence and horizontal transport may be compared. As a result, although a large precipitation amount is observed with very high SSTs, it does not significantly correlate with SST over moderately warm sea surfaces. Various studies indicate that SST works as a threshold for the precipitation activity (e.g., Gadgil et al. 1984 ). In the

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Shoichi Shige, Yukari N. Takayabu, Satoshi Kida, Wei-Kuo Tao, Xiping Zeng, Chie Yokoyama, and Tristan L’Ecuyer

and a cooling peak at low levels. The resulting MCS heating profile is positive at all levels but with a maximum value in the upper troposphere (“top heavy” profile). Hartmann et al. (1984) demonstrated with a simple linear global model that the top-heavy heat source produces a Walker circulation that is in much better agreement with observations than those that are produced with a more conventional heat source having a maximum value in the middle troposphere. Recently, Schumacher et al. (2004

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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

also been detected (e.g., chlorophyll: Waliser et al. 2005 ; ozone: Tian et al. 2007 ; aerosols: Tian et al. 2008 ). The quasi-periodic occurrence of the MJO provides a primary source for the predictability of tropical atmosphere on subseasonal time scales, which may bridge the forecasting gap between medium- to long-range weather forecast and short-term climate prediction (e.g., Waliser et al. 2006 ; Jiang et al. 2008 ). Therefore, the improved understanding of the fundamental features of the

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