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

a reference. The bias correction ranges from 10% to 28% at low levels within the boundary layer and 8% to 20% from 800 to 300 hPa. The validation of the bias correction was done by comparing the corrected radiosonde data with independent ground-based GPS TCWV at six sites in the Sahel. The comparison shows that the mean difference between the two datasets ranges between −1 and 1.5 kg m −2 , which is close to the uncertainty of the GPS TCWV data (±1 kg m −2 ). Clearly, the use of corrected

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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

a result, most MCS processes are represented in these large-scale models by subgrid parameterizations. Our current understanding of these processes is limited and this affects the formulation and basic concepts underlying their parameterizations. For instance, the major impact of cold pools on MCS life cycles, via their influences on further convective triggering and MCS propagation, is well recognized ( Houze and Betts 1981 ; Corfidi 2003 ). However, a comprehensive formulation of cold pools

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

surface evaporation, and other processes (see, e.g., Eltahir 1998 ). Wallace and Holwill (1997) have indicated that in the vicinity of Niamey most of the evaporation occurs during the first day directly after rain. Currently, it is not realistic to ask the operational NWP models to represent this type of feedback in terms of precipitation forecasting in West Africa as the diurnal variation of the atmospheric boundary layer in this area is complex ( Parker et al. 2005 ). However, it is important to

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Adrian M. Tompkins and Laura Feudale

North Atlantic and ENSO regions was demonstrated. Despite shortcomings in SST prediction in some regions, the DEMETER forecasts of precipitation were found useful for predicting malaria incidence in Botswana at 3-month lead times ( Thomson et al. 2006 ). It should be pointed out that ENSO is generally accepted to have a greater impact on southern African rainfall than in the AMMA region of West Africa ( Ropelewski and Halpert 1987 ; Nicholson and Selato 2000 ). An evaluation of the current (as of

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

(s) between developing and nondeveloping waves, primarily from the viewpoint of synoptic-scale structure and dynamics, is the focus of the current paper. This will be accomplished through the intensive study of three NAMMA waves: wave 2, which developed into Tropical Storm Debby within the NAMMA domain; wave 7, which developed into a depression within the NAMMA region and which later became Hurricane Helene beyond the NAMMA region; and wave 4, which remained a nondeveloping wave as it traversed the NAMMA

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O. Bock and M. Nuret

during the AMMA EOP. However, the assessment of NWP models makes sense only when independent observations are used. Hence, in the present work we use precipitable water vapor (PWV) estimates provided by a network of ground-based global positioning system (GPS) receivers, the data of which are not presently assimilated into the currently used NWP models. The GPS technique is known to provide very accurate estimates of PWV (usually considered at the level 1–2 kg m −2 ) with high temporal resolution

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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

bias present in the data is removed, the analysis will be improved. b. Impact on the wind field It is also interesting to study the changes in the wind field, particularly at the level of the African easterly jet (AEJ). It is found that the AEJ changes if the configuration of the radiosonde network is changed. Figure 7 presents the lower boundary of the AEJ (i.e., the zonal wind at 700 hPa). Differences between AMMA and PREAMMA ( Fig. 7 , top right) show an increase in the AEJ on the southeastern

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Peter Knippertz and Andreas H. Fink

model version T159L60 started at 0000 UTC of the first day of each of the GPCP pentads (see section 2a ) is considered, which results in a perfect temporal match. Note that this resolution is considerably coarser than the current model version T799L91. The data were retrieved from the ECMWF archive at 1° × 1° latitude–longitude horizontal resolution and then interpolated onto the GPCP 2.5° × 2.5° grid using a bicubic interpolation routine contained in the Climate Data Operators software package

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