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Fatima Karbou, Florence Rabier, Jean-Philippe Lafore, Jean-Luc Redelsperger, and Olivier Bock

Hemisphere seems to emphasize the moistening over India, South America, and in western and central Africa in monsoon regions. On the other hand, EXP5 also emphasizes drying over Saudi Arabia and over the desert regions of northeast Africa. The drying or moistening of the atmosphere is far from being negligible (cf. the maps in Figs. 9a and 9b for the relative changes in TCWV), reaching +10% and 20% over wet and desert regions, respectively. The results from EXP4 and EXP6 are quite similar to those of

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Anna Agustí-Panareda, Anton Beljaars, Carla Cardinali, Iliana Genkova, and Chris Thorncroft

. This brings an increase in temperature in the analysis, notably at nighttime. Overall, the wind analysis increments are against the prevalent southwesterly monsoon flow ( Fig. 3b ), particularly in the Sahel. This is consistent with a reduction in the north–south temperature gradient seen here and the associated reduction in the north–south pressure gradient (not shown). It is also worth noting that around several stations in the Sahel (e.g., Timbuktu, Mali; N’Djamena, Chad; and Agadez, Niger) the

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Sen Chiao and Gregory S. Jenkins

1. Introduction Our current understanding of tropical cyclogenesis (TC-genesis in the extreme eastern Atlantic remains an important challenge because of the potential dangers that are posed to downstream communities in the Caribbean, Central America, and the United States. Developing tropical cyclones also pose a danger to commercial shipping, local fishermen, and ferry services in coastal regions of western Africa. Most tropical cyclones form from an intensification of the African easterly

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Françoise Guichard, Nicole Asencio, Christophe Peugeot, Olivier Bock, Jean-Luc Redelsperger, Xuefeng Cui, Matthew Garvert, Benjamin Lamptey, Emiliano Orlandi, Julia Sander, Federico Fierli, Miguel Angel Gaertner, Sarah C. Jones, Jean-Philippe Lafore, Andrew Morse, Mathieu Nuret, Aaron Boone, Gianpaolo Balsamo, Patricia de Rosnay, Bertrand Decharme, Philip P. Harris, and J.-C. Bergès

(2006) for simulations over North America using horizontal resolutions of about 10 to a few 10s of kilometers. It is currently unknown how accurately mesoscale models depict water budgets over West Africa, and how they compare to each other in their simulations of individual MCSs. This study aims to document this issue using results from an intercomparison of mesoscale models conducted within the African Monsoon Multidisciplinary Analysis (AMMA) program ( Redelsperger et al. 2006 ). The study

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Benjamin Sultan, Serge Janicot, and Cyrille Correia

uniform modulation of convection within the African ITCZ. It is associated with a modulation of the zonal low-level wind over the equatorial Atlantic and a zonal dipole of convection between Africa and the north equatorial Atlantic off the coast of South America ( Mounier et al. 2008 ). The second mode (hereafter the Sahelian mode) is a westward-propagating signal from eastern Africa to the western tropical Atlantic, consistent with the signal already detected over the Sahel ( Sultan et al. 2003 ). On

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