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Yu Zhang, Wenyu Huang, and Deyu Zhong

. The complex atmospheric circulation conditions and the roles as an ecological barrier and as the water tower of China make the Sanjiangyuan region a key region on the TP. A detailed investigation of the hydrological processes of the region contributes to the formulation of effective strategies for regional ecosystem and water resource conservation. As the atmospheric moisture transport process is an important part of the hydrological cycle, knowledge of where moisture comes from (moisture sources

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Xiuzhen Li, Wen Zhou, Chongyin Li, and Jie Song

-reaching influence of such extreme precipitation fluctuations, there is an urgent need to investigate the physical processes and mechanisms that govern precipitation variability over south China. Sufficient moisture supply is necessary for precipitation generation. The precipitation amount over a region usually depends on the available moisture arising from two main sources: local evaporation and externally advective moisture. The latter is much more important than the former because, even on the most extensive

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David J. Raymond and Željka Fuchs

intraseasonal time scales compared to the untuned version of Raymond (2001) . The weak temperature gradient approximation when applied to a single-column model approximates the effect of the tropical environment by forcing the column to maintain buoyancy equilibrium with its surroundings via an imposed vertical velocity profile that counters heating with diabatic cooling. This vertical velocity, along with the convergence and divergence it implies, also transports moisture. Grabowski (2001 , 2003) found

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Maria J. Molina and John T. Allen

1. Introduction Boundary layer moisture is vital for tornadic thunderstorm development ( Galway 1979 ; Hagemeyer 1991 ; Doswell et al. 1996 ). Therefore, identifying the source regions and processes governing moisture advection can improve our understanding of the physical drivers responsible for their occurrence. Operational forecasters and researchers have recognized the Gulf of Mexico (GoM) as an important source of moisture for tornadic storms in the contiguous United States (CONUS) for

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Randal D. Koster, Zhichang Guo, Rongqian Yang, Paul A. Dirmeyer, Kenneth Mitchell, and Michael J. Puma

1. Introduction Most land surface models (LSMs) used with atmospheric general circulation models (AGCMs) keep track of the moisture state of the soil with a prognostic (state) variable called “soil moisture” or “soil wetness,” typically defined at a number of vertical subsurface levels. Given the general dearth of in situ large-scale observations of soil moisture, this model-generated quantity is often made available to the scientific community as a data product. The National Centers for

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Adam R. Cornwell and L. D. Danny Harvey

1. Introduction The prediction of soil moisture in climate models and in operational forecasting follows two distinctly different paradigms. The paradigm used in climate models makes use of the surface energy balance. The more recent implementations of this approach distinguish between evaporation from wet leaves, from inside leaves (through the stomata), and from the bare ground surface. The driving force is taken as the difference between saturation vapor pressure at the surface temperature

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Hua Su and Robert E. Dickinson

1. Background Land–atmosphere interactions contribute significantly in the warm season to regional extreme weather and climate (e.g., floods or droughts) ( Beljaars et al. 1996 ; Giorgi et al. 1996 ; Bosilovich and Sun 1999 ; Pal and Eltahir 2002 , 2003 ). Among the land hydrologic variables involved, soil moisture is arguably most important for its effects on a wide range of energy and moisture processes and, hence, the evolution of both local and remote atmosphere. Midtropospheric

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Vivek K. Arora and George J. Boer

al. 1998 ) and the dynamic treatment of vegetation (e.g., Foley et al. 1996 ; Arora 2002 ). The role of LSMs is to mediate the fluxes of energy, moisture, and momentum that connect the atmosphere to the underlying land surface. Soil moisture is the dominant quantity affecting these surface fluxes. Shukla and Mintz (1982) highlight the role played by soil moisture in the extratropics and make an analogy with energy in the ocean. The ocean stores some of the radiational energy it receives in

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Jie Jiang, Tianjun Zhou, Hailong Wang, Yun Qian, David Noone, and Wenmin Man

responsible for precipitation trends over central Asia. Fig . 1. Twenty-five moisture source regions tagged in this study. NAO: Arctic Ocean; NATL: northern North Atlantic; TATL: tropical Atlantic; SATL: South Atlantic; ABS: Arabian Sea; BOB: Bay of Bengal; SWIO: southwestern Indian Ocean; SEIO: southeastern Indian Ocean; SCS: South China Sea; NPAC: North Pacific; SPAC: South Pacific; MEDI: Mediterranean; NEURO: northern Europe; WEURO: western Europe; SEURO: southern Europe; NCA: northern central Asia

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Richard I. Cullather and Michael G. Bosilovich

et al. 2000 ). An initial evaluation of a reanalysis record is therefore a useful undertaking. The purpose of this study is to provide a basic overview of the quality of MERRA in polar regions. To this end we focus on the atmospheric moisture budget, which has recently been the subject of other studies. A companion paper examines the representation of the atmospheric energy budget in MERRA over high latitudes (Cullather and Bosilovich 2011, manuscript submitted to J. Climate ). The surface

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