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Song Yang, S-H. Yoo, R. Yang, K. E. Mitchell, H. van den Dool, and R. W. Higgins

1. Introduction It is widely recognized that, in addition to sea surface temperature (SST), soil moisture provides a strong forcing for governing atmospheric processes on various time scales (see reviews in Betts et al. 1996 ; Dirmeyer et al. 1999 ; Yang and Lau 2006 ; Koster et al. 2006 ). In the midlatitude continents, it may be the most important boundary condition during warm seasons (e.g., Koster and Suarez 1995 ; Lau and Bua 1998 ; Koster et al. 2000 ), especially in relatively dry

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Jinwon Kim and Hyun-Suk Kang

1. Introduction Orography in California, which is characterized by two nearly parallel two-dimensional (2D) mountain ranges, the Coastal Range and the Sierra Nevada, plays an important role in shaping the regional water cycle through terrain-induced wind disturbances. It is well known that winter rainfall in California is primarily generated by orographic lifting of moisture-rich low-level inflow from the eastern Pacific over the western slopes of these mountain ranges ( Chen et al. 1994

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Ana M. B. Nunes and John O. Roads

1. Introduction Many studies have focused on the adjustment of moisture and divergence analyses (e.g., Krishnamurti et al. 1984 , 1988 , 1991 ; Donner 1988 ; Heckley et al. 1990 ; Puri and Miller 1990 ; Puri and Davidson 1992 ; Aonashi 1993 ; Kasahara et al. 1994 ; Manobianco et al. 1994 ; Yap 1995 ; Treadon 1996 ) in order to improve precipitation forecasts. Some of these studies have used observed rain rates to directly adjust the moisture and diabatic heating profiles to

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Binayak P. Mohanty and Jianting Zhu

1. Introduction Moisture flux across the land–atmosphere boundary (through infiltration, evaporation, and plant transpiration) is an important component of large-scale hydroclimatic processes. Predicting the mean flux rate for a remote sensing footprint or model grid/pixel is usually a primary concern in most practical soil–vegetation–atmospheric transfer (SVAT) models. One of the key land–atmosphere linkages is described by Koster et al. (2004) , whose results from a recent model

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Xia Zhang, Shu Fen Sun, and Yongkang Xue

simulations (e.g., Cox et al. 1999 ; Viterbo et al. 1999 ; Smirnova et al. 2000 ; Poutou et al. 2004 ). For example, comparisons of results from the Project for Intercomparison of Land Surface Parameterization Schemes Phase 2(d) [PILPS 2(d)] have shown that the models with an explicit frozen soil scheme give a much more realistic soil temperature simulation during winter than those without a frozen scheme ( Luo et al. 2003 ). A frozen soil model with realistic simulation of soil temperature, moisture

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Kevin E. Trenberth, Lesley Smith, Taotao Qian, Aiguo Dai, and John Fasullo

1. Introduction Driven mainly by solar heating, water is evaporated from ocean and land surfaces, transported by winds, and condensed to form clouds and precipitation that falls to land and oceans. Precipitation over land may be stored temporarily as snow or soil moisture, while excess rainfall runs off and forms streams and rivers, which discharge the freshwater into the oceans, thereby completing the global water cycle ( Fig. 1 ). Associated with this water cycle, energy, salt within the

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Xi Chen, Yongqin David Chen, and Zhicai Zhang

of treating soil moisture below the root zone as groundwater, which is used as a “boundary condition” in the simulation of soil moisture dynamics. In river hydraulics and hydrodynamics of open channels, a porous subsurface is seldom considered to be an active participant of in-channel processes and dynamics. In atmospheric science, soil moisture and groundwater are represented as “buckets” of limited sizes in which water movement is not coupled with streamflow dynamics. For other scientists and

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Richard G. Lawford, John Roads, Dennis P. Lettenmaier, and Phillip Arkin

state of the surface as represented by soil moisture is critical in determining the heat and moisture fluxes to the atmosphere. Papers in the third section of this special issue deal with global and regional water budgets, which are also an integrating theme of GEWEX. This summary paper is intended to provide the reader with a broader perspective and understanding of GEWEX as well as a context for the detailed papers that follow. GEWEX is organized into three research domains: modeling and

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J. Li, X. Gao, and S. Sorooshian

et al. 2005 ). In addition to testing physics processes to be used in the run, we also tested the soil moisture spinup issue using the month of July 1999. Liang et al. (2004) argued that 1 month of spinup is sufficient for their long-term (20 yr) runs. For the 1-month test runs, we examined soil moisture variations with no spinup and with 5-, 10-, 20-, and 30-day spinup. Figure 3 shows the daily soil moisture variations in the topsoil layer (10 cm) and the third soil layer (60 cm), which are

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Guoxiong Wu, Yimin Liu, Qiong Zhang, Anmin Duan, Tongmei Wang, Rijin Wan, Xin Liu, Weiping Li, Zaizhi Wang, and Xiaoyun Liang

)]. Scientists and visiting scholars at the University of California, Los Angeles (UCLA) headed by Professor M. Yanai evaluated the TP heating source ( Yanai et al. 1973 , 1992 ; Yanai and Li 1994 ; Shen et al. 1984 ; Liou and Zhou 1987 ; Nitta 1983 ; Luo and Yanai 1983 , 1984 ; He et al. 1987 ) and studied the seasonal changes in the large-scale circulation, thermal structure, and heat sources and moisture sinks over the Tibetan Plateau and the surrounding areas ( Yanai et al. 1992 ). They also

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