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Robert S. Ross, T. N. Krishnamurti, S. Pattnaik, and A. Simon

1. Introduction African easterly waves (AEWs) are known to play a significant role in the development of Atlantic tropical cyclones. Avila et al. (2000) found that on average 62% of all Atlantic tropical depressions develop from AEWs. From June through October of the 1996 season Avila et al. tracked 62 AEWs. Only 12 of these waves developed into tropical depressions, but all 12 of these became named systems. It is evident that a majority of AEWs never develop beyond the wave stage, but that

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

: On the significance of African easterly waves on convection. J. Climate , 19 , 5405 – 5421 . 10.1175/JCLI3920.1 Parker, D. J. , and Coauthors , 2008 : The AMMA radiosonde programme and its implications for the future of atmospheric monitoring over Africa. Bull. Amer. Meteor. Soc. , 89 , 1015 – 1027 . 10.1175/2008BAMS2436.1 Rabier, F. , Järvinen H. , Klinker E. , Mahfouf J-F. , and Simmons A. , 2000 : The ECMWF operational implementation of four-dimensional variational

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Adrian M. Tompkins and Laura Feudale

. , Leutbecher M. , Rodwell M. J. , Vitart F. , and Balsamo G. , 2008 : Advances in simulating atmospheric variability with the ECMWF model: From synoptic to decadal time-scales. Quart. J. Roy. Meteor. Soc. , 134 , 1337 – 1352 . 10.1002/qj.289 Berry, G. J. , and Thorncroft C. , 2005 : Case study of an intense African easterly wave. Mon. Wea. Rev. , 133 , 752 – 766 . 10.1175/MWR2884.1 Blanke, B. , and Delecluse P. , 1993 : Variability of the tropical Atlantic Ocean simulated by a

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Ryan D. Torn

1. Introduction African easterly waves (AEWs) are synoptic-scale waves that propagate westward through sub-Saharan Africa during the Northern Hemisphere summer ( Burpee 1972 ). These waves are important to this region because they provide a significant fraction of seasonal rainfall and are often associated with mesoscale convective systems (e.g., Payne and McGarry 1977 ; Fink and Reiner 2003 ). Once over the Atlantic Ocean, AEWs also provide seed disturbances for tropical cyclones ( Avila and

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Xuefeng Cui, Douglas J. Parker, and Andrew P. Morse

1. Introduction This paper investigates the atmospheric surface layer response to the frequency of rainfall events and the subsequent drying out of the land surface. It will show that the frequency of rainfall events is important for keeping temperatures within a critical range for the survivability of mosquitoes and thus influences the transmission of malaria. The notion of coupling between evaporation and precipitation (e.g., Mintz and Serafini 1992 ) has been developed to show that a

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Sen Chiao and Gregory S. Jenkins

waves (AEWs), which propagate westward from western Africa toward the North Atlantic and the Caribbean Sea in the range of 10°–20°N ( Hopsch et al. 2007 ; Avila and Pasch 1992 ; Pasch and Avila 1994 ). For instance, during 1999, Tropical Storm Cindy formed off the coast of Senegal ( Sall and Sauvageot 2005 ) with reports of more than 100 fishermen fatalities in Senegal, Gambia, and Mauritania. In general, most convective activity [i.e., ensembles of more or less organized short-lived convective

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C. Faccani, F. Rabier, N. Fourrié, A. Agusti-Panareda, F. Karbou, P. Moll, J.-P. Lafore, M. Nuret, F. Hdidou, and O. Bock

, provide indirect information about the atmospheric temperature and humidity structure with a relatively coarse vertical resolution, compared to radiosonde profiles. Furthermore, they are more difficult to use over land than over sea and, as a consequence, are only partially used over land. Only high-peaking channels, describing the stratosphere and upper troposphere, are generally assimilated. Information about the lower troposphere is then lacking from satellite data over the African continent

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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

. 10.1175/2008JHM1068.1 Bechtold, P. , and Coauthors , 2008 : Advances in simulating atmospheric variability with the ECMWF model: From synoptic to decadal time-scales. Quart. J. Roy. Meteor. Soc. , 134 , 1337 – 1351 . 10.1002/qj.289 Betts, A. K. , and Miller M. J. , 1986 : A new convective adjustment scheme. Part II: Single column tests using GATE wave, BOMEX, ATEX and arctic air-mass data sets. Quart. J. Roy. Meteor. Soc. , 112 , 693 – 709 . Bock, O. , Guichard F. , Janicot S

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

1. Introduction The West African monsoon (WAM) is still far from being well represented in numerical weather prediction (NWP) models. The WAM is governed by multiple mechanisms, which show very complex interactions that are not yet fully understood. Not surprisingly, a realistic representation of the spatial distribution, the strength, and the duration of the WAM remains a great challenge. The atmospheric water vapor is responsible for the cloud formation and plays a crucial role in convection

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Benjamin Sultan, Serge Janicot, and Cyrille Correia

. Dell’Aquila, A. , Lucarini V. , Ruti P. M. , and Calmanti S. , 2005 : Hayashi spectra of the Northern Hemisphere mid-latitude atmospheric variability in the NCEP–NCAR and ECMWF reanalyses. Climate Dyn. , 25 , 639 – 652 . 10.1007/s00382-005-0048-x Diedhiou, A. , Janicot S. , and Laurent H. , 1999 : Easterly wave regimes and associated convection over West Africa and the tropical Atlantic: Results from NCEP/NCAR and ECMWF reanalyses. Climate Dyn. , 15 , 795 – 822 . 10.1007/s

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