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Venkataramana Sridhar, Kenneth G. Hubbard, Jinsheng You, and Eric D. Hunt

1. Introduction Soil moisture plays a vital role in linking drought, climate, and vegetation. Soil moisture data, collected from depths below the surface over the long term as well as at higher temporal and spatial resolutions, are valuable for assessing the extent and severity of drought quite accurately. There are also a variety of drought indices and a thorough description on their tractability, transparency, sophistication, extendability, and dimensionality is given by Keyantash and Dracup

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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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Roberto Mera, Arlene G. Laing, and Frederick Semazzi

1. Introduction Weather and climate in the African Sahel are dominated by two major wind systems: the southwesterly West African monsoon (WAM) and the northeasterly (harmattan) trade winds emanating from the Sahara Desert. As the primary driver for precipitation, the WAM is a vital component of the socioeconomic environment of the region. In addition to the agricultural benefit of the rains, the public health sector is affected through the relationship between the onset of monsoon moisture and

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John D. Frye and Thomas L. Mote

. 2003 ; Trier et al. 2004 ; Holt et al. 2006 ). Studies have shown that when distinct surface heterogeneities were present, mesoscale circulation patterns developed similar to the mesoscale circulation patterns evident during a land–sea breeze ( Pielke 2001 ; Chaboureau et al. 2004 ). One surface characteristic that has been shown to create these patterns is soil moisture, which is the focus of the present study. Soil moisture heterogeneities also have been shown to have a feedback to

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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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Feng Hu and Tim Li

planetary zonal scale (e.g., Knutson et al. 1986 ; Lau and Chan 1986 ; Hendon and Salby 1994 ; Wheeler and Kiladis 1999 ; Kiladis et al. 2009 ; Li and Zhou 2009 ; Lau and Lau 2010 ; Li 2014 ). Various theories (e.g., Emanuel 1987 ; Wang and Rui 1990 ) have been developed to understand the MJO eastward propagation. The most recent widely accepted one is the moisture mode theory, which emphasizes the important role of MJO-scale moisture perturbation in the propagation dynamics (e.g., Maloney

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Liang Guo, Ruud J. van der Ent, Nicholas P. Klingaman, Marie-Estelle Demory, Pier Luigi Vidale, Andrew G. Turner, Claudia C. Stephan, and Amulya Chevuturi

1. Introduction East Asia (EA) is one of the most populated areas in the world. Understanding and predicting EA precipitation is essential for agriculture and socioeconomic development. East Asia is located over the eastern part of the Eurasian continent, spanning from the tropics to the temperate zones; its precipitation is linked to oceanic and terrestrial moisture sources across these regions. EA precipitation varies over time due to natural variability and human impacts, which can lead to

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Qianwen Luo and Wen-wen Tung

1. Introduction Atmospheric rivers (ARs) are narrow channels of enhanced moisture flux in the atmosphere ( Newell et al. 1992 ; Zhu and Newell 1994 ). They perform ocean-to-ocean and ocean-to-land moisture transports ( Newman et al. 2012 ), accounting for >90% of the total meridional moisture flux in the midlatitudes ( Zhu and Newell 1998 ). They are typically parts of the warm conveyor belts (WCBs), which are strongly ascending airstreams near winter extratropical cyclones. The WCBs transport

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