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Peter J. Lamb, Diane H. Portis, and Abraham Zangvil

1. Introduction Central to atmospheric behavior on a range of space and time scales is the relative importance of horizontal water vapor advection versus the vertical moisture flux from the earth’s land and ocean surfaces. At the small-scale extreme, the interaction of these moisture sources and their associated thermodynamic and dynamic processes contributes to the development of shallow cumulus clouds (e.g., Krishnamurti et al. 1980 ; Rabin et al. 1990 ; Chen and Avissar 1994 ; Berg and

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M. Issa Lélé, Lance M. Leslie, and Peter J. Lamb

most limiting parameters for sustaining life, agriculture, and economic development in the sub-Saharan West African countries. Therefore, the role played by the atmospheric moisture transfer and its phase transitions through evaporation, latent heat release, and associated energy transports and exchanges are of central importance for the WAM dynamics and variability. This is because hydrological processes play an important role in determining the scales of the major circulation patterns (e

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Susan Stillman, Xubin Zeng, and Michael G. Bosilovich

5, respectively), the uncertainty is still high ( Sillmann et al. 2013 ; Geil et al. 2013 ). Soil moisture is another major component of the terrestrial water cycle and is driven by precipitation. It helps regulate the surface energy balance by affecting the partitioning of available energy flux into latent and sensible heat fluxes at the surface, particularly in moisture-limited regions. Gravimetric measurement is the most accurate way to measure soil moisture, but this only represents a point

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Thomas Engel, Andreas H. Fink, Peter Knippertz, Gregor Pante, and Jan Bliefernicht

lesser extent, from evaporation at the continental surface. A convergent humidity flux [with the specific humidity q (kg kg −1 ) and horizontal wind vector (m s −1 )] then causes an accumulation of moisture in the atmospheric column as TPW (kg m −2 ): where p sfc (hPa) is the surface pressure and g = 9.81 m s −2 the gravitational acceleration. The convective available potential energy (CAPE; J kg −1 ; Emanuel 1994 ) is a common measure of convective instability: Here, α pcl and α env

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Lisa Hannak, Peter Knippertz, Andreas H. Fink, Anke Kniffka, and Gregor Pante

; Paxian et al. 2016 ). Moreover, Marsham et al. (2013) and Birch et al. (2014) show that issues in the diurnal cycle of latent heating and cloud radiative forcing impact on the north–south pressure gradient and thus the northward advection of moisture from the south to the Sahel. One element of the WAM that has received relatively little attention so far is the extensive cover of low- and midlevel clouds over southern West Africa (SWA) during the peak summer monsoon from July to September (JAS

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Robert A. Clark III, Zachary L. Flamig, Humberto Vergara, Yang Hong, Jonathan J. Gourley, Daniel J. Mandl, Stuart Frye, Matthew Handy, and Maria Patterson

years, the number of spaceborne instruments collecting data available to Earth scientists has grown (e.g., Ungar et al. 2003 ; Friedl et al. 2002 ; Tapley et al. 2004 ). It is now feasible, even routine, to access estimates of precipitation, potential evapotranspiration, land use, land cover, topography, soil moisture, and other variables collected from space in a timely fashion. Moreover, these datasets are often available for free regardless of geopolitical boundaries. Multiple studies have

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Kerry H. Cook and Edward K. Vizy

over Africa ( Vizy and Cook 2002 ; Hagos and Cook 2007 ; Patricola and Cook 2010 , 2011 ), although it fails in midlatitude applications where transients must be included on the lateral boundary. Simulations on this domain with synoptically varying boundary conditions confirm the usefulness of the climate-mode approach. The six, year-long 20C simulations have different initial conditions, as detailed in Cook and Vizy (2012) . A 9-month spinup period is used to allow the soil moisture, which is

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John G. Dwyer, Michela Biasutti, and Adam H. Sobel

timing of tropical precipitation; and a reduction of soil moisture early in the year in monsoon regions delaying monsoonal precipitation. Most of this work focuses on the projected amplitude changes, especially for precipitation. Projected phase changes have received less attention and are not as well understood. We are interested in what modifies the annual cycles of both precipitation and surface temperature in the greenhouse gas–forced, fully coupled models. In this paper we address a more limited

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Gang Zhang, Kerry H. Cook, and Edward K. Vizy

heat of water vaporization, q is the specific humidity, g is the gravity acceleration, and z is the geopotential height. MSE increasing with altitude indicates a stable atmosphere. Analysis of the MSE allows one to distinguish between the roles of temperature and moisture variations in changing atmospheric stability properties. MSE analysis is widely used in studying instability associated with rainfall (e.g., Pu and Cook 2012 ; Neupane and Cook 2013 ). Figure 8a displays profiles of MSE

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Gang Zhang, Kerry H. Cook, and Edward K. Vizy

other parameterizations remain in the model. Most relevant to the production of rainfall, these parameterizations include schemes for determining heat, moisture, and momentum transport from the planetary boundary layer (PBL) and calculations of the cloud microphysics. As described in section 3 , two sensitivity simulations using different PBL and cloud microphysics schemes are used to evaluate the dependence of the default simulation on these parameterizations. Here we note that results shown in

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