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On the late northward propagation of the West African monsoon in summer 2006 in the region of Niger/Mali / Philippe Drobinski in Journal of geophysical research : Atmospheres, vol 114 n° D9 (2009)
[article]
Titre : On the late northward propagation of the West African monsoon in summer 2006 in the region of Niger/Mali Type de document : Article/Communication Auteurs : Philippe Drobinski, Auteur ; Sophie Bastin, Auteur ; Serge Janicot, Auteur ; Olivier Bock , Auteur ; A. Dabas, Auteur ; P. Delville, Auteur ; O. Reitebuch, Auteur ; Benjamin Sultan, Auteur Année de publication : 2009 Projets : AMMA & AMMA-2 / Janicot, Serge Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Afrique occidentale
[Termes IGN] données GPS
[Termes IGN] données météorologiques
[Termes IGN] Mali
[Termes IGN] mousson
[Termes IGN] NigerRésumé : (auteur) This paper investigates the fine‐scale dynamical processes at the origin of the late northward migration of the monsoon flow in summer 2006 in the region of Niger and Mali (onset on 3 July 2006 compared to the climatological onset date, 24 June). Compared to a 28‐year climatology, 2006 NCEP‐2 reanalyses show evidence of an anomalous pattern during 10 days between 25 June and 3 July 2006, characterized by the African Easterly Jet (AEJ) blowing from the northeast along a narrow northeast/southwest band located over the Hoggar and Air mountains associated with an unusually strong northeasterly harmattan in the lee of the mountains. Using data collected during the African Monsoon Multidisciplinary Analysis (AMMA) experiment and mesoscale numerical simulations, this study shows evidence of interaction between the AEJ and the orography supported by the reduced gravity shallow water theory which explains the enhancement of the harmattan downstream of the Hoggar and Air mountains in summer 2006. The enhanced harmattan contributes to move southward the intertropical discontinuity (ITD) defined as the interface between the cool moist southwesterly monsoon flow and the warm dry harmattan. Finally, an interaction between the ITD and African Easterly waves contributes to propagate the ITD southward retreat about 1500 km to the west of the Hoggar and Air mountains. Numéro de notice : A2009-594 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2008JD011159 Date de publication en ligne : 13/05/2009 En ligne : https://doi.org/10.1029/2008JD011159 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96202
in Journal of geophysical research : Atmospheres > vol 114 n° D9 (2009)[article]West African Monsoon observed with ground-based GPS receivers during African Monsoon Multidisciplinary Analysis (AMMA) / Olivier Bock in Journal of geophysical research : Atmospheres, vol 113 n° D21 (16 November 2008)
[article]
Titre : West African Monsoon observed with ground-based GPS receivers during African Monsoon Multidisciplinary Analysis (AMMA) Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Marie-Noëlle Bouin , Auteur ; Erik Doerflinger, Auteur ; Philippe Collard, Auteur ; Florian Masson, Auteur ; Rémi Meynadier, Auteur ; Samuel Nahmani , Auteur ; et al., Auteur Année de publication : 2008 Projets : AMMA & AMMA-2 / Janicot, Serge Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Afrique occidentale
[Termes IGN] circulation atmosphérique
[Termes IGN] données GPS
[Termes IGN] erreur systématique
[Termes IGN] humidité de l'air
[Termes IGN] modèle de simulation
[Termes IGN] mousson
[Termes IGN] phénomène atmosphérique
[Termes IGN] précipitation
[Termes IGN] vapeur d'eau
[Termes IGN] variation saisonnièreRésumé : (auteur) A ground-based GPS network has been established over West Africa in the framework of African Monsoon Multidisciplinary Analysis (AMMA) in tight cooperation between French and African institutes. The experimental setup is described and preliminary highlights are given for different applications using these data. Precipitable water vapor (PWV) estimates from GPS are used for evaluating numerical weather prediction (NWP) models and radiosonde humidity data. Systematic tendency errors in model forecasts are evidenced. Correlated biases in NWP model analyses and radiosonde data are evidenced also, which emphasize the importance of radiosonde humidity data in this region. PWV and precipitation are tightly correlated at seasonal and intraseasonal timescales. Almost no precipitation occurs when PWV is smaller than 30 kg m−2. This limit in PWV also coincides well with the location of the intertropical discontinuity. Five distinct phases in the monsoon season are determined from the GPS PWV, which correspond either to transition or stationary periods of the West African Monsoon system. They may serve as a basis for characterizing interannual variability. Significant oscillations in PWV are observed with 10- to 15-day and 15- to 20-day periods, which suggest a strong impact of atmospheric circulation on moisture and precipitation. The presence of a diurnal cycle oscillation in PWV with marked seasonal evolutions is found. This oscillation involves namely different phasing of moisture fluxes in different layers implying the low-level jet, the return flow, and the African Easterly Jet. The broad range of timescales observed with the GPS systems shows a high potential for investigating many atmospheric processes of the West African Monsoon. Numéro de notice : A2008-656 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2008JD010327 Date de publication en ligne : 05/11/2008 En ligne : https://doi.org/10.1029/2008JD010327 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98266
in Journal of geophysical research : Atmospheres > vol 113 n° D21 (16 November 2008)[article]Correction of humidity bias for Vaïsala RS80 sondes during AMMA 2006 Observing Period / Mathieu Nuret in Journal of Atmospheric and Oceanic Technology, vol 25 n° 11 (November 2008)
[article]
Titre : Correction of humidity bias for Vaïsala RS80 sondes during AMMA 2006 Observing Period Type de document : Article/Communication Auteurs : Mathieu Nuret, Auteur ; Jean-Philippe Lafore, Auteur ; Françoise Guichard, Auteur ; Jean-Luc Redelsperger, Auteur ; Olivier Bock , Auteur ; Anna Agusti-Panareda, Auteur ; Jean-Blaise N’Gamini, Auteur Année de publication : 2008 Article en page(s) : pp 2152 - 2158 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Afrique occidentale
[Termes IGN] données GPS
[Termes IGN] données météorologiques
[Termes IGN] erreur systématique
[Termes IGN] humidité de l'air
[Termes IGN] mousson
[Termes IGN] radiosondageRésumé : (autuer) During the African Monsoon Multidisciplinary Analyses (AMMA) program, which included a special observing period that took place over West Africa in 2006, a major effort was devoted to monitor the atmosphere and its water cycle. The radiosonde network was upgraded and enhanced, and GPS receivers deployed. Among all sondes released in the atmosphere, a significant number were Vaisala RS80-A sondes, which revealed a significant dry bias relative to Vaisala RS92 (a maximum of 14% in the lower atmosphere, reaching 20% in the upper levels). This paper makes use of a simple but robust statistical approach to correct the bias. Comparisons against independent GPS data show that the bias is almost removed at night, whereas for daytime conditions, a weak dry bias (5%) still remains. The correction enhances CAPE by a factor of about 4 and, thus, becomes much more in line with expected values over the region. Numéro de notice : A2008-570 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1175/2008JTECHA1103.1 Date de publication en ligne : 01/11/2008 En ligne : https://doi.org/10.1175/2008JTECHA1103.1 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103427
in Journal of Atmospheric and Oceanic Technology > vol 25 n° 11 (November 2008) . - pp 2152 - 2158[article]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)
[article]
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] moussonRésumé : (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
in Annales Geophysicae > vol 26 n° 9 (September 2008) . - pp 2569 - 2595[article]Use of a Kalman filter for the retrieval of surface BRDF coefficients with a time-evolving model based on the ECOCLIMAP land cover classification / O. Samain in Remote sensing of environment, vol 112 n° 4 (15/04/2008)
[article]
Titre : Use of a Kalman filter for the retrieval of surface BRDF coefficients with a time-evolving model based on the ECOCLIMAP land cover classification Type de document : Article/Communication Auteurs : O. Samain, Auteur ; J.L. Roujeau, Auteur ; Bernhard Geiger, Auteur Année de publication : 2008 Article en page(s) : pp 1337 - 1346 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] Afrique occidentale
[Termes IGN] cohérence des données
[Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF
[Termes IGN] filtre de Kalman
[Termes IGN] image SPOT-Végétation
[Termes IGN] image Terra-MODIS
[Termes IGN] occupation du sol
[Termes IGN] réflectance de surface
[Termes IGN] réflectance directionnelle
[Termes IGN] variation saisonnièreRésumé : (Auteur) The goal of this study is to demonstrate the asset in using a Kalman filter to improve the spatial coherence and time consistency of surface Bidirectional Reflectance Distribution Function (BRDF) and albedo retrievals from moderate resolution sensor data sets. For this purpose, we use a simple surface model describing BRDF seasonal evolution for the land cover classes of the ECOCLIMAP database. The application of temporal composition windows used so far for BRDF retrieval is limited in regions characterized by a high frequency of cloud coverage, which induces a lot of gaps in the temporal series. Instead, the present method ensures a continuous production of surface BRDF parameters thanks to the Kalman filter recursive data processing. An application of the method is performed with SPOT/VEGETATION data over the western Africa equatorial region for the year 2003. Compared to presently available products from VEGETATION and MODIS instruments, this new approach allows to fill the gaps and improves the retrieved parameters time consistency. Another interesting possibility of the Kalman filter is the production of surface biophysical variables in quasi-real-time for applications that require a frequent update of the surface parameters. Copyright Elsevier Numéro de notice : A2008-092 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2007.07.007 En ligne : https://doi.org/10.1016/j.rse.2007.07.007 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29087
in Remote sensing of environment > vol 112 n° 4 (15/04/2008) . - pp 1337 - 1346[article]A method for soil moisture estimation in Western Africa based on the ERS scatterometer / Mehrez Zribi in IEEE Transactions on geoscience and remote sensing, vol 46 n° 2 (February 2008)PermalinkAssessment of water budgets computed from NWP models and observational datasets during AMMA-EOP / Olivier Bock (2008)PermalinkSpectral normalisation and fusion of optical sensors for the retrieval of BRDF and albedo: application to vegetation, MODIS, and MERIS data sets / O. Samain in IEEE Transactions on geoscience and remote sensing, vol 44 n° 11 Tome 1 (November 2006)PermalinkAMMA, une étude multidisciplinaire de la mousson ouest-africaine / Jean-Luc Redelsperger in La Météorologie, n° 54 ([01/10/2006])PermalinkElaboration d'un modèle prédictif des risques de transmission paludique / Roland Ngom in Géomatique expert, n° 52 (01/09/2006)PermalinkAfrica environment outlook / United nations environment programme (2002)PermalinkIntérêt des radars satellitaires pour l'exploration géologique et minière sur des territoires de socles anciens : Afrique de l'ouest et Guyane française, le projet Aurros / Anne Bourguignon (01/03/2001)PermalinkProjet SIAP, système d'information et d'analyse des pèches / D. Berthier (1999)PermalinkCartographie à 1:200.000 réalisé par l'IGN dans les pays francophones d'Afrique centrale et d'Afrique de l'ouest / Alain Jaloux (1996)PermalinkRégionalisation du bilan hydrique à l'aide de mesures satellitaires pour l'étude du fonctionnement des écosystèmes de l'Afrique de l'ouest / O. Amram (1996)PermalinkTélédétection de l'environnement dans l'espace francophone / F. Bonn (1994)PermalinkApport des données satellitaires en vue de l'estimation de la production primaire nette à l'échelle régionale / P. Loudjani (1993)PermalinkMise en valeur agricole des bas-fonds au Sahel : Typologie, fonctionnement hydrologique, potentialités agricoles / J. Albergel (1993)PermalinkAnalysis of vegetation seasonal evolution and mapping of forest cover in West Africa with the use of NOAA AVHRR HRPT data / Frédéric Achard in Photogrammetric Engineering & Remote Sensing, PERS, vol 56 n° 10 (october 1990)PermalinkLa lutte contre l'ensablement (Bulletin de Informations et documents) / M. GuimbertPermalinkEtude spatiale de la biosphère terrestre / Nicolas Viovy (1990)PermalinkAVHRR for monitoring global tropical deforestation / J.P. Malingreau in International Journal of Remote Sensing IJRS, vol 10 n°4-5 (May 1989)PermalinkMapping the ground Albedo of western Africa and its time evolution during 1984 using Meteosat visible data / L. Diabate in Remote sensing of environment, vol 27 n° 3 (01/03/1989)PermalinkEtudes des rythmes saisonniers de la végétation en Afrique de l'ouest par télédétection spatiale / Frédéric Achard (1989)PermalinkLe rôle des cultures commerciales dans l'évolution de la société senoufo, Sud du Mali / B. Sanoko (1989)Permalink