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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]Radiosonde humidity bias correction over the West African region for the special AMMA reanalysis at ECMWF / Anna Agustí‐Panareda in Quarterly Journal of the Royal Meteorological Society, vol 135 n° 640 (April 2009 part A)
[article]
Titre : Radiosonde humidity bias correction over the West African region for the special AMMA reanalysis at ECMWF Type de document : Article/Communication Auteurs : Anna Agustí‐Panareda, Auteur ; Drasko Vasiljevic, Auteur ; Anton Beljaars, Auteur ; Olivier Bock , Auteur ; Françoise Guichard, Auteur ; et al., Auteur Année de publication : 2009 Projets : AMMA & AMMA-2 / Janicot, Serge Article en page(s) : pp 595 - 617 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Afrique (géographie physique)
[Termes IGN] erreur systématique
[Termes IGN] mousson
[Termes IGN] radiosondage
[Termes IGN] teneur en vapeur d'eauRésumé : (auteur) During the African Monsoon Multidisciplinary Analysis (AMMA) field experiment in 2006 there was a large increase in the number of radiosonde data over West Africa. This has the potential of improving the numerical weather prediction (NWP) analysis/forecast and the water budget studies over that region. However, it is well known that the humidity from radiosondes can have some errors depending on sonde type, relative humidity (RH), temperature and the age of the sensor and can give rise to dry biases that are typically between 5% and 30% for RH. Three main sonde types were used in the AMMA field experiment: Vaisala RS80A, Vaisala RS92 and MODEM. In this article, a new empirical method is presented by using the operational European Centre for Medium‐Range Weather Forecasts (ECMWF) short‐range forecast as an intermediary dataset for computing biases. The validation of the correction method using global positioning system (GPS) total columnar water vapour (TCWV) confirms that the method is able to correct for a large part of the dry biases associated with the different sonde types. Results from analysis experiments show how the correction of humidity is particularly important in the West African region due to its impact on the development of convection in NWP models. The proposed radiosonde humidity bias correction has been applied to the special AMMA reanalysis experiment performed at ECMWF for the 2006 West African wet monsoon season. This is expected to benefit a wide number of AMMA‐related studies that make use of the reanalysis, in particular those focusing on the water cycle. Numéro de notice : A2009-574 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1002/qj.396 Date de publication en ligne : 23/03/2009 En ligne : https://doi.org/10.1002/qj.396 Format de la ressource électronique : URL bulletin Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96190
in Quarterly Journal of the Royal Meteorological Society > vol 135 n° 640 (April 2009 part A) . - pp 595 - 617[article]Mission AMMA : L'apport de l'IGN / Olivier Bock in IGN magazine, n° 51 (janvier - février 2009)
[article]
Titre : Mission AMMA : L'apport de l'IGN Type de document : Article/Communication Auteurs : Olivier Bock , Auteur Année de publication : 2009 Projets : AMMA & AMMA-2 / Janicot, Serge Article en page(s) : pp 6 - 14 Langues : Français (fre) Descripteur : [Termes IGN] Afrique (géographie physique)
[Termes IGN] moussonNuméro de notice : A2009-571 Affiliation des auteurs : LAREG (1991-2011) Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102524
in IGN magazine > n° 51 (janvier - février 2009) . - pp 6 - 14[article]Réservation
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[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)PermalinkAssessment of water budgets computed from NWP models and observational datasets during AMMA-EOP / Olivier Bock (2008)PermalinkComparison of ground-based GPS precipitable water vapour to independent observations and NWP model reanalyses over Africa / Olivier Bock in Quarterly Journal of the Royal Meteorological Society, vol 133 n° 629 (Octobre 2007 part B)PermalinkAssessment of GPS data for meteorological applications over Africa: Study of error sources and analysis of positioning accuracy / Andrea Walpersdorf in Journal of Atmospheric and Solar-Terrestrial Physics, vol 69 n° 12 (August 2007)PermalinkAMMA, une étude multidisciplinaire de la mousson ouest-africaine / Jean-Luc Redelsperger in La Météorologie, n° 54 ([01/10/2006])PermalinkEstimation of the horizontal velocity of the Socotra eddy and some observations of sea surface thermal features using Insat-1b / M.M. Ali in International Journal of Remote Sensing IJRS, vol 11 n° 1 (January 1990)PermalinkMonsoon flood boundary delineation and damage assessment using space borne imaging radar and Landsat data / M.L. Imhoff in Photogrammetric Engineering & Remote Sensing, PERS, vol 53 n° 4 (april 1987)PermalinkLa répartition des pluies et les régimes pluviométriques au Cameroun / J.B. Suchel (1972)Permalink