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

emissivity biases (due to rain, snow, etc.) are more likely to occur over high-latitude areas. Such effects can potentially diminish the assimilation experiment’s impacts. One should bear in mind that the observations from AMSU-B channels 2 and 5 and from AMSU-A channel 4 are normally either entirely rejected or assimilated over open sea only. Over land, additional conditions are applied to reject observations over high-altitude areas (greater than 1000 m) or if the departures from a first guess are

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O. Bock and M. Nuret

smoothed by the integrative effect of interpolation from the surrounding grid points. Nevertheless, it is expected and confirmed from Fig. 4 that the agreement decreases with coarser resolution (decrease in slope and slight increase in standard deviation). The reduction in bias at most sites is actually an artifact resulting from the above-mentioned compensating effects. The increase in bias at Dakar might be due to the impact of grid points over the ocean. We must also mention that there is an

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Sen Chiao and Gregory S. Jenkins

account for the possible local/regional circulations due to topography effects. As shown in Fig. 3a , the highest elevations over Guinea Highlands are more than 1300 m. The nested domain of TER used 30-min-resolution (∼54 km) data, and the highest elevation was approximately 300 m over the Guinea Highlands ( Fig. 3b ). In the nested domain of NOTER, all topography was removed to further illustrate the role of the Guinea Highlands. 4. Results a. The structure and evaluation of MCSs and TD-4 formation

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Adrian M. Tompkins and Laura Feudale

incorrect representation of short-term variability in the model implies that statistical corrections for subseasonal variability may also be required if the model is to be used to drive end-user models such as regional crop models, as the total seasonal yield in rainfall-limited (non irrigated) regions depends strongly on the variability of the rainfall and not just the mean amount ( Challinor et al. 2003 ). To focus on the AMMA SOP onset, Fig. 7 shows a time–latitude plot of rainfall for the 1 May

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Peter Knippertz and Andreas H. Fink

, KF08 hypothesized that the strong extratropical influences may imply a comparably good predictability of such events that would allow a timely warning of the population and therefore a mitigation of detrimental impacts as well as an exploitation of beneficial effects. To test this hypothesis, the present study gives a statistical evaluation of boreal winter precipitation forecasts made by the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis project (ERA-40; Uppala et

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Ryan D. Torn

.1002/qj.49711147002 Hsieh, J-S. , and Cook K. H. , 2007 : A study of the energetics of African easterly waves using a regional climate model. J. Atmos. Sci. , 64 , 421 – 440 . 10.1175/JAS3851.1 Janjić, Z. I. , 1994 : The step-mountain eta coordinate model: Further developments of the convection, viscous sublayer, and turbulence closure schemes. Mon. Wea. Rev. , 122 , 927 – 945 . 10.1175/1520-0493(1994)122<0927:TSMECM>2.0.CO;2 Kain, J. S. , and Fritsch J. M. , 1990 : A one

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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

radiosonde sites, the relevance of vertical high-resolution soundings, and the effects of a humidity bias correction are assessed. The paper is organized as follows. Sections 2 and 3 of this paper describe the data processing and the model setup. The results of the assimilation diagnostics and forecast performance are discussed, respectively, in sections 4 and 5 . Conclusions are presented in section 6 . 2. Data processing Figure 1 shows the distribution of the western African GTS radiosonde

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Benjamin Sultan, Serge Janicot, and Cyrille Correia

1. Introduction West African societies depend heavily on summer monsoon rainfall, especially in the Sahel where rain-fed crop production is the main source of food and income of one of the world’s most rapidly growing populations ( Baron et al. 2005 ). Predicting the fluctuations of the West African monsoon would be greatly beneficial to regional agriculture and water resource management. The distribution of rainfall within the rainy season is of particular importance to agricultural strategy

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