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Adrian M. Tompkins and Laura Feudale

throughout most of JJA. The skill of predicting the seasonal mean rainfall anomaly in JAS has improved over time in tandem with improvements in the quality of the ocean analysis as Atlantic Ocean monitoring increases. Examining the temporal variability of the daily rainfall, the observations showed a clear spectral peak associated with intermittent African easterly wave activity and a separate peak at 15 days, both of which have been documented previously. The model was unable to reproduce these spectral

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

500 hPa, that is, the layer that comprises the monsoon flow and the African easterly jet. In this layer, aircraft provide information of wind and temperature in the ascending and descending phases close to the airports. Surface pressure and daytime 2-m humidity observations are assimilated from synoptic observations (SYNOPs) over land, ships, and buoys. Over the ocean, the 10-m wind and 2-m nighttime humidity are also assimilated from buoys. Observed temperature, wind, and humidity profiles from

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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

types of radiosondes were used during the 2006 AMMA campaign, and since the Nuret et al. (2008) method has to date only been performed on the Vaisala RS80-A, the Agusti-Panareda et al. (2009) scheme was preferred for this study. In fact, their approach gives a bias correction for all radiosonde types over our area of interest. The humidity correction is a linear combination of four sine waves (Fourier transforms) calculated by matching the cumulative distribution functions (CDFs) of the RH

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

information content, gave a valuable description of the temperature and humidity at different levels in the atmosphere. The use of these measurements in NWP has led to substantial progress being made, but more effort is needed to assimilate many more observations in a wide range of atmospheric situations (clear, cloudy) and with a variety of surface conditions (ocean, land, snow, etc.). However, many issues are still to be addressed, in particular, the assimilation of observations in the presence of

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

. Figure 2 illustrates the daily rainfall amounts with 3-hourly satellite rainfall estimation using the National Oceanic and Atmospheric Administration/Climate Prediction Center (NOAA/CPC) Morphing Technique (CMORPH; information online at ). A rain belt is observed on 26 July, ranging from the coastal area in Guinea to northern Nigeria with a pronounced rainfall center in southeast Mali, western Niger, Burkina Faso, and northern

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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

evapotranspiration, together with atmospheric water transport, is required for an accurate estimation of water budgets (e.g.; Drusch and Viterbo 2007 ). Such estimates, therefore, require the modeling of atmospheric processes and land–ocean–atmosphere interactions over a range of temporal and spatial scales. For example, the diurnal cycle of solar radiation over West Africa is responsible for very significant diurnal modulations of atmospheric convection, whether dry, moist, shallow, or deep precipitating

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Benjamin Sultan, Serge Janicot, and Cyrille Correia

1974, the National Oceanic and Atmospheric Administration’s (NOAA) polar-orbiting Television and Infrared Observation Satellite (TIROS) has enabled the establishment of a quasi-complete series of twice-daily measures of OLR at the top of the atmosphere and at a resolution of 2.5° latitude–longitude ( Grueber and Krueger 1984 ). The Interpolated OLR dataset ( Liebmann and Smith 1996 ) provided by the Climate Diagnostics Center has been used here. In tropical areas, deep convection and rainfall can

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