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Adrian M. Tompkins and Laura Feudale

prediction of the El Niño–Southern Oscillation (ENSO) phenomenon and the associated SST anomalies in the eastern Pacific, but the influence of these anomalies is less significant in West Africa than in many other tropical regions ( Ropelewski and Halpert 1987 ; Paeth and Friederichs 2004 ). Second, another oceanic region that is important for West African rainfall, especially in the coastal countries, is the tropical Atlantic. Because of the strong three-way interaction between SST anomalies, surface

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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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O. Bock and M. Nuret

framework of the African Monsoon Multidisciplinary Analyses (AMMA; information online at http://www.amma-international.org ), NWP models thus play a crucial role in many scientific research areas. One of the main objectives of AMMA is that of improving our knowledge of land, ocean, and atmosphere processes and the interactions of the West African monsoon (WAM) system ( Redelsperger et al. 2006 ). The skill of NWP models in predicting rainfall over West Africa, and the tropics in general, is especially

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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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Sen Chiao and Gregory S. Jenkins

–vortex near the western African coastline. Model forecasts of the AEW associated with Tropical Storm Debby were used to address the items above with an emphasis placed on aspects of the MCS–vortex before tropical cyclogenesis in association with the AEW–MCS transition from continental to oceanic environments from 19 to 21 August 2006. There is a discussion on the spatial structure and temporal evolution of the pre–TD 4 environment during 19–21 August in section 2 . The numerical model and experiment

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Fatima Karbou, Elisabeth Gérard, and Florence Rabier

1. Introduction Microwave observations from the Advanced Microwave Sounding Unit-A and -B [AMSU-A and -B; or Microwave Humidity Sounder (MHS)] instruments have been widely used in numerical weather prediction (NWP) to improve the initial conditions for short-range forecasts. AMSU instruments are on board low-orbiting satellites such as the different generations of the National Oceanic and Atmospheric Administration (NOAA) satellites, the National Aeronautics and Space Administration’s (NASA

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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 http://www.cpc.ncep.noaa.gov/products/janowiak/cmorph_description.html ). 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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Peter Knippertz and Andreas H. Fink

) Operational Vertical Sounder (TOVS) and outgoing longwave radiation precipitation index (OPI) data from the National Oceanic and Atmospheric Administration (NOAA) series of satellites. The gauge data are assembled and analyzed by the Global Precipitation Climatology Centre (GPCC) of the German Weather Service (Deutscher Wetterdienst, DWD) and by the Climate Prediction Center of NOAA. The blending procedure is described in Adler et al. (2003) . Here, the pentad product that provides precipitation

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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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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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