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Abdou L. Dieng, Saidou M. Sall, Laurence Eymard, Marion Leduc-Leballeur, and Alban Lazar

1. Introduction African easterly waves (AEWs) are synoptic-scale disturbances observed between the surface and midtroposphere from East (Sudan, Central African Republic, Chad) to West Africa (Niger, Nigeria, Burkina Faso, Mali) up to the Senegalese and Guinea coasts. They are the dominant synoptic weather systems in West Africa and the tropical Atlantic during boreal summer and modulate rainfall in West Africa in relation with the mesoscale convective systems (MCSs) ( Reed et al.1977 ; Fink

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Elinor R. Martin and Chris Thorncroft

easterly wave, diurnally varying convection, and a convectively coupled atmospheric kelvin wave . Mon. Wea. Rev. , 140 , 1108 – 1124 , doi: 10.1175/MWR-D-11-00122.1 . Voldoire , A. , and Coauthors , 2013 : The CNRM-CM5.1 global climate model: Description and basic evaluation . Climate Dyn. , 40 , 2091 – 2121 , doi: 10.1007/s00382-011-1259-y . Volodin , E. , N. Dianskii , and A. Gusev , 2010 : Simulating present-day climate with the INMCM4.0 coupled model of the atmospheric and

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

characteristics and hitherto poorly documented atmospheric dynamics of these events. Only the Ouagadougou rainfall event is briefly discussed in Cornforth et al. (2017) as an example of an African easterly wave (AEW) breaking event, and a synoptic overview is given in Galvin (2010) . The paper is structured as follows. Section 2 gives a detailed description of the gauge, satellite, and reanalysis data used in this study, including their advantages and limitations. Section 3 describes the methods to

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Rosalind Cornforth, Douglas J. Parker, Mariane Diop-Kane, Andreas H. Fink, Jean-Philippe Lafore, Arlene Laing, Ernest Afiesimama, Jim Caughey, Aida Diongue-Niang, Abdou Kassimou, Peter Lamb, Benjamin Lamptey, Zilore Mumba, Ifeanyi Nnodu, Jerome Omotosho, Steve Palmer, Patrick Parrish, Leon-Guy Razafindrakoto, Wassila Thiaw, Chris Thorncroft, and Adrian Tompkins

activity are modulated not only by synoptic systems like African easterly waves, but also at longer intraseasonal time scales (10–90 days). These subseasonal modes of variability are mostly controlled by convectively coupled equatorial waves, midlatitude atmospheric intrusions, as well as the Madden–Julian oscillation (MJO). They influence the onset of the rainy season and have an important impact on agricultural yields in the Sahel. The progress made in subseasonal forecasting (chapter 7) emphasizes

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

either collocated with topographical features or located far from topography allowing locally generated atmospheric instability to dominate the diurnal cycle. Applying a 50 mm day −1 threshold to the rainfall at 0300 UTC averaged over the NN domain and at 0000 UTC over the SN domain, 12 extreme events (see Table 1 ) from the summer of 2006 are selected. Of the 12 events, 4 are associated with African easterly waves (AEWs) as indicated by 700-hPa wind and relative vorticity fields (not shown). The

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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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Wassila M. Thiaw and Vadlamani B. Kumar

in agricultural production and river flow. The National Oceanic and Atmospheric Administration (NOAA)’s Climate Prediction Center (CPC) began to provide USAID FEWS with real-time gauge-based 10-day weather summaries to enable operational monitoring of crop conditions. However, given the difficulty to access rain gauge measurements from Africa, CPC also began to provide USAID FEWS with access to real-time satellite rainfall estimates to improve the weather summaries and to enable effective

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Kerry H. Cook and Edward K. Vizy

simulations. The purpose of this paper is to better understand the precipitation changes that lead to these simulated reductions in growing-season days over East Africa, since a physical understanding of the change is useful for evaluating confidence in the projections. Background on East African rainy seasons is provided in the next section, along with an overview of projected changes from increased atmospheric greenhouse gas concentrations. The regional model simulations are described and their realism

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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

the development of new hydrological modeling software: EF5. EF5 is a framework encompassing multiple hydrological model cores, including but not limited to the grid cell–based water balance component of CREST, linear reservoir routing as implemented in CREST, routing using the kinematic wave assumption ( Chow et al. 1988 ), and the Sacramento family of water balance models ( Burnash et al. 1973 ). EF5 accepts the same input file formats as the CREST model and adds support for GeoTIFF (tagged image

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