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Operational meteorology in West Africa : observational networks, weather analysis and forecasting / Andreas H. Fink in Atmospheric Science Letters, vol 12 n° 1 (January - March 2011)  

Public [article]  inAtmospheric Science Letters > vol 12 n° 1 (January - March 2011) . - pp 135 - 141 Titre : Operational meteorology in West Africa : observational networks, weather analysis and forecasting Type de document : Article/Communication Auteurs : Andreas H. Fink, Auteur ; Anna Agustí‐Panareda, Auteur ; Douglas J. Parker, Auteur ; Jean-Philippe Lafore, Auteur ; Jean-Blaise Ngamini, Auteur ; Ernest Afiesimama, Auteur ; Anton Beljaars, Auteur ; Olivier Bock , Auteur ; Michael Christoph, Auteur ; Francis Didé, Auteur ; et al., Auteur Année de publication : 2011 Article en page(s) : pp 135 - 141 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Afrique occidentale [Termes IGN] coordonnées GPS [Termes IGN] données météorologiques [Termes IGN] modèle météorologique [Termes IGN] mousson [Termes IGN] prévision météorologique [Termes IGN] radiosondage [Termes IGN] teneur intégrée en vapeur d'eau Résumé : (Auteur) Real‐time surface and upper‐air observations are crucial to the analysis and forecasting of the West African monsoon (WAM). This paper will focus on the African Monsoon—Multidisciplinary Analyses (AMMA)‐driven reactivation and modernisation of the radiosonde network over West Africa, its potential long‐term impact on upper‐air operations in the region, the influence of the additional data in WAM analyses and forecasting, and the AMMA‐related development and usage of the West African Analysis/Forecasting (WASA/F) forecast method. Numéro de notice : A2011-594 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1002/asl.324 Date de publication en ligne : 22/02/2011 En ligne : https://doi.org/10.1002/asl.324 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91518 [article]

Global 4DVAR assimilation and forecast experiments using AMSU observations over land. Part II: Impacts of assimilating surface-sensitive channels on the African monsoon during AMMA / Fatima Karbou in Weather and Forecasting, vol 25 n° 1 (February 2010)    

Public [article]  inWeather and Forecasting > vol 25 n° 1 (February 2010) . - pp Titre : Global 4DVAR assimilation and forecast experiments using AMSU observations over land. Part II: Impacts of assimilating surface-sensitive channels on the African monsoon during AMMA Type de document : Article/Communication Auteurs : Fatima Karbou, Auteur ; Florence Rabier, Auteur ; Jean-Philippe Lafore, Auteur ; Jean-Luc Redelsperger, Auteur ; Olivier Bock , Auteur Année de publication : 2010 Article en page(s) : pp Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Afrique occidentale [Termes IGN] assimilation des données [Termes IGN] coordonnées GPS [Termes IGN] données météorologiques [Termes IGN] emissivité [Termes IGN] étude de faisabilité [Termes IGN] humidité de l'air [Termes IGN] image NOAA-AMSU [Termes IGN] mousson [Termes IGN] prévision météorologique Résumé : (auteur) Observations from Advanced Microwave Sounding Unit-A and -B (AMSU-A and -B) have been more intensively used over sea than over land because of large uncertainties about the land surface emissivity and the skin temperature. Several methods based on a direct estimation of the land emissivity from satellite observations have been found to be very useful for improving the assimilation of sounding channels over land. Feasibility studies have been conducted within the Météo-France global assimilation system in order to examine the possibility of assimilating low-level atmospheric observations receiving a contribution from the land surface. The present study reports on three 2-month assimilation and forecast experiments, which include the assimilation of surface-sensitive observations from AMSU-A and -B together with a control experiment, which represents the operational model. The assimilation experiments have been compared with the control, and important changes in the analyzed atmospheric fields and in the precipitation forecasts over parts of the tropics, and especially over West Africa, have been noticed. The experiments seem to emphasize the atmospheric moistening in India, South America, and in West Africa, together with atmospheric drying over Saudi Arabia and northeast Africa. The drying or moistening of the atmosphere has been successfully evaluated using independent measurements from the GPS African Monsoon Multidisciplinary Analysis (AMMA) network. Precipitation and OLR forecasts have also been examined and compared with independent measurements. Physically, the changes result in a better-organized African monsoon with a stronger ITCZ in terms of ascent, vorticity, and precipitation, but there is no northward shift of the monsoon system. Low-level humidity observations have been found to have important impacts on the analysis and to produce positive impacts on forecast scores over the tropics. Numéro de notice : A2010-664 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1175/2009WAF2222244.1 Date de publication en ligne : 01/02/2010 En ligne : https://doi.org/10.1175/2009WAF2222244.1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91770 [article]

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The impacts of AMMA radiosonde data on the French global assimilation and forecast system / C. Faccani in Weather and Forecasting, vol 24 n° 5 (October 2009)  

Public [article]  inWeather and Forecasting > vol 24 n° 5 (October 2009) . - pp 1268 - 1286 Titre : The impacts of AMMA radiosonde data on the French global assimilation and forecast system Type de document : Article/Communication Auteurs : C. Faccani, Auteur ; Florence Rabier, Auteur ; Nadia Fourrié, Auteur ; A. Agusti-Panareda, Auteur ; Fatima Karbou, Auteur ; Patrick Moll, Auteur ; Jean-Philippe Lafore, Auteur ; Mathieu Nuret, Auteur ; F. Hdidou, Auteur ; Olivier Bock , Auteur Année de publication : 2009 Article en page(s) : pp 1268 - 1286 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] assimilation des données [Termes IGN] humidité de l'air [Termes IGN] mousson [Termes IGN] prévision météorologique [Termes IGN] radiosondage Résumé : (auteur) The high vertical density soundings recorded during the 2006 African Monsoon Multidisciplinary Analysis (AMMA) campaign are assimilated into the French numerical weather prediction Action de Recherche Petite Echelle Grande Echelle (ARPEGE) four-dimensional variational data assimilation (4DVAR) system, with and without a bias correction for relative humidity. Four different experiments are carried out to assess the impacts of the added observations. The analyses and forecasts from these different scenarios are evaluated over western Africa. For the full experiment using all data together with a bias correction, the humidity analysis is in better agreement with surface observations and independent GPS observations than it was for the other experiments. AMMA data also improve the African easterly jet (AEJ) on its southeasterly side, and when they are used with an appropriate bias correction, the daily and monthly averaged precipitation results are in relatively good agreement with the satellite-based precipitation estimates. Forecast scores are computed with respect to surface observations, radiosondes, and analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF). The positive impacts of additional radiosonde observations (with a relevant bias correction) are found to propagate downstream with a positive impact over Europe at the 2–3-day forecast range. Numéro de notice : A2009-607 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1175/2009WAF2222237.1 Date de publication en ligne : 01/10/2009 En ligne : https://doi.org/10.1175/2009WAF2222237.1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102426 [article]

Multiscale analysis of precipitable water vapor over Africa from GPS data and ECMWF analyses / Olivier Bock in Geophysical research letters, vol 34 n° 9 (16 May 2007)  

Public [article]  inGeophysical research letters > vol 34 n° 9 (16 May 2007) . - 6 p. Titre : Multiscale analysis of precipitable water vapor over Africa from GPS data and ECMWF analyses Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Françoise Guichard, Auteur ; Serge Janicot, Auteur ; Jean-Philippe Lafore, Auteur ; Marie-Noëlle Bouin , Auteur ; Benjamin Sultan, Auteur Année de publication : 2007 Projets : 1-Pas de projet / Article en page(s) : 6 p. Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Afrique (géographie physique) [Termes IGN] analyse multiéchelle [Termes IGN] données GPS [Termes IGN] données météorologiques [Termes IGN] précipitation [Termes IGN] vapeur d'eau Résumé : (auteur) This is the first climatological analysis of precipitable water vapor (PWV) from GPS data over Africa. The data reveal significant modulations and variability in PWV over a broad range of temporal scales. GPS PWV estimates are compared to ECMWF reanalysis ERA40. Both datasets show good agreement at the larger scales (seasonal cycle and inter‐annual variability), driven by large scale moisture transport. At intra‐seasonal (15–40 days) and synoptic (3–10 days) scales, strong PWV modulations are observed from GPS, consistently with ECMWF analysis. They are shown to be correlated with convection and the passage of equatorial waves and African Easterly waves. The high‐frequency GPS observations also reveal a significant diurnal cycle in PWV, which magnitude and spectral content depends strongly on geographic location and shows a seasonal modulation. The diurnal cycle of PWV is poorly represented in ERA40 reflecting weaknesses in the water cycle of global circulation models at this timescale. Numéro de notice : A2007-682 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2006GL028039 Date de publication en ligne : 09/05/2007 En ligne : https://doi.org/10.1029/2006GL028039 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95742 [article]