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An intercomparison of simulated rainfall and evapotranspiration associated with a mesoscale convective system over West Africa / Françoise Guichard in Weather and Forecasting, vol 25 n° 1 (February 2010)    

Public [article]  inWeather and Forecasting > vol 25 n° 1 (February 2010) . - pp Titre : An intercomparison of simulated rainfall and evapotranspiration associated with a mesoscale convective system over West Africa Type de document : Article/Communication Auteurs : Françoise Guichard, Auteur ; Nicole Asencio, Auteur ; Christophe Peugeot, Auteur ; Olivier Bock , Auteur ; et al., Auteur Année de publication : 2010 Article en page(s) : pp Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] Afrique occidentale [Termes IGN] analyse comparative [Termes IGN] évapotranspiration [Termes IGN] modèle de simulation [Termes IGN] objet meso structurel [Termes IGN] orage [Termes IGN] précipitation Résumé : (auteur) An evaluation of precipitation and evapotranspiration simulated by mesoscale models is carried out within the African Monsoon Multidisciplinary Analysis (AMMA) program. Six models performed simulations of a mesoscale convective system (MCS) observed to cross part of West Africa in August 2005. Initial and boundary conditions are found to significantly control the locations of rainfall at synoptic scales as simulated with either mesoscale or global models. When initialized and forced at their boundaries by the same analysis, all models forecast a westward-moving rainfall structure, as observed by satellite products. However, rainfall is also forecast at other locations where none was observed, and the nighttime northward propagation of rainfall is not well reproduced. There is a wide spread in the rainfall rates across simulations, but also among satellite products. The range of simulated meridional fluctuations of evapotranspiration (E) appears reasonable, but E displays an overly strong zonal symmetry. Offline land surface modeling and surface energy budget considerations show that errors in the simulated E are not simply related to errors in the surface evaporative fraction, and involve the significant impact of cloud cover on the incoming surface shortwave flux. The use of higher horizontal resolution (a few km) enhances the variability of precipitation, evapotranspiration, and precipitable water (PW) at the mesoscale. It also leads to a weakening of the daytime precipitation, less evapotranspiration, and smaller PW amounts. The simulated MCS propagates farther northward and somewhat faster within an overall drier atmosphere. These changes are associated with a strengthening of the links between PW and precipitation. Numéro de notice : A2010-645 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1175/2009WAF2222250.1 Date de publication en ligne : 01/02/2010 En ligne : https://doi.org/10.1175/2009WAF2222250.1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90741 [article]

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Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006 / Serge Janicot in Annales Geophysicae, vol 26 n° 9 (September 2008)  

Public [article]  inAnnales Geophysicae > vol 26 n° 9 (September 2008) . - pp 2569 - 2595 Titre : Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006 Type de document : Article/Communication Auteurs : Serge Janicot, Auteur ; Chris Thorncroft, Auteur ; A. Ali, Auteur ; Nicole Asencio, Auteur ; Gérard Berry, Auteur ; Olivier Bock , Auteur ; et al., Auteur Année de publication : 2008 Projets : AMMA & AMMA-2 / Janicot, Serge Article en page(s) : pp 2569 - 2595 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Afrique occidentale [Termes IGN] circulation atmosphérique [Termes IGN] mousson Résumé : (auteur) The AMMA (African Monsoon Multidisciplinary Analysis) program is dedicated to providing a better understanding of the West African monsoon and its influence on the physical, chemical and biological environment regionally and globally, as well as relating variability of this monsoon system to issues of health, water resources, food security and demography for West African nations. Within this framework, an intensive field campaign took place during the summer of 2006 to better document specific processes and weather systems at various key stages of this monsoon season. This campaign was embedded within a longer observation period that documented the annual cycle of surface and atmospheric conditions between 2005 and 2007. The present paper provides a large and regional scale overview of the 2006 summer monsoon season, that includes consideration of of the convective activity, mean atmospheric circulation and synoptic/intraseasonal weather systems, oceanic and land surface conditions, continental hydrology, dust concentration and ozone distribution. The 2006 African summer monsoon was a near-normal rainy season except for a large-scale rainfall excess north of 15° N. This monsoon season was also characterized by a 10-day delayed onset compared to climatology, with convection becoming developed only after 10 July. This onset delay impacted the continental hydrology, soil moisture and vegetation dynamics as well as dust emission. More details of some less-well-known atmospheric features in the African monsoon at intraseasonal and synoptic scales are provided in order to promote future research in these areas. Numéro de notice : A2008-599 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/angeo-26-2569-2008 Date de publication en ligne : 01/09/2008 En ligne : https://doi.org/10.5194/angeo-26-2569-2008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103433 [article]