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101. Recent climatological trend of the Saharan heat low and its impact on the West African climate

Author: Lavaysse, Christophe, primary, Flamant, Cyrille, additional, Evan, Amato, additional, Janicot, Serge, additional, and Gaetani, Marco, additional
Published: 2015
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102. Intraseasonal variability of the ocean - atmosphere coupling in the Gulf of Guinea during boreal spring and summer

Author: De Coëtlogon, Gaëlle, Janicot, Serge, Lazar, Alban, ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Processus de la variabilité climatique tropicale et impacts (PARVATI), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), European Community’s Sixth Framework Research Programme, Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636))
Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], statistical analysis, Statistical analysis, Air-sea interactions, air-sea interactions, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
Abstract: Statistical analyses of the satellite TMI sea-surface temperature (SST) and QuikSCAT surface winds in boreal spring and summer are performed to investigate the intraseasonal variability of air sea interactions in die Gulf of Guinea There, empirical orthogonal function decomposition shows the existence of peaks around IS days. and their lagged cross-correlation the signature of an expected 5-day lag wind forcing and 3-day lag strong negative SST feedback Lagged linear regressions are performed onto a reference SST index of the cold tongue northern front in the Gulf of Guinea. A cold SST anomaly covering the equatorial and coastal upwelling is forced after about one week by stronger-than-usual south-easterlies linked to the Si Helena anticyclone. suggesting that intraseasonal variability in the Gull of Guinea is connected to large-scale fluctuations in the South Atlantic Within about 5 degrees S and 5 degrees N, two retroactions between SST and surface wind appear to dominate near-surface atmosphere conditions When the wind leads the SST. stronger monsoonal winds north of 2 degrees N are partly sustained by die developing SST anomaly and bring more humidity and rainfall toward the continent When the SST leads Lie wind, a reversal of anomalous winds is observed mainly south of 2 degrees N. closing a negative feedback loop with a biweekly periodicity Eventually. further in with an ocean model emphasizes the contribution of the horizontal advection in shaping these intraseasonal SST signals The contribution of vertical processes may also be important but was more difficult to estimate Copyright (C) 2010 Royal Meteorological Society
Published: 2010
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103. Links between African easterly waves, midlatitude circulation and intraseasonal pulsations of the West African heat low

Author: Lavaysse, C., Flamant, C., Janicot, Serge, Knippertz, P., SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), School of Earth and Environment [Leeds] (SEE), University of Leeds, Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)
Subjects: ECMWF ERA-40 reanalyses, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, ECMWF ERA-40, West African monsoon, tropical convection, reanalyses, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes, Tropical convection, Satellite-derived brightness temperature, AMMA, satellite-derived brightness temperature
Abstract: During summer 2006. the intensity of the thermal depression over the Sahara. derived from European Centre for Medium-range Weather Forecast analyses. exhibited a strong decrease during the first couple of weeks of September Simultaneously. widespread convective activity over the Sahel was detected. The aims of this study are to identify the reasons for this decrease of the West African Heat Low (WAHL) activity, to discuss the possible relationship with convection and to assess the representativity of such an event at the climatological tune-scale. From spectral analysis of the daily WAHL thickness during summer 2006. two period bands of significant intraseasonal pulsations were identified. and confirmed using the ERA-40 reanalysis. namely 3-10d and 10-30d In both the 2006 case-study and the climatological composite study. we find that detrimental conditions in the 3-10d period band are associated with moist and cool advections in the lower troposphere linked to the southerly sector of African easterly waves (AEWs) which increase convective activity over the Sahel These humid and cold advections from the south are more pronounced when the AEW interacts with a midlatitude depression In the 10-30d period band. the impact of midlatitude circulation is demonstrated During the collapsing period of the 10-30d pulsations of the WAHL thickness, an upper-level trough is seen over northern West Africa This situation generates a surge of 700 hPa cold air from Libya into the Sahara. an increase of the 925 hPa anticyclonic circulation and a significant increase of convective activity over the Sahel Copyright (C) 2010 Royal Meteorological Society
Published: 2010
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104. Impacts of the Mediterranean basins on the West African monsoon: observed connection patterns (1979

Author: Rodriguez de Fonseca, Belen, Fontaine, Bernard, Garcia-Serrano, Javier, Roucou, Pascal, Losada, Theresa, Chauvin, Fabrice, Gervois, Sebastien, Sijikumar, Sivarajan, Ruti, Paolo-M, Janicot, Serge, Centre de Recherches de Climatologie ( CRC ), Université de Bourgogne ( UB ) -Centre National de la Recherche Scientifique ( CNRS ), and Fontaine, Bernard
Subjects: [SDE.MCG] Environmental Sciences/Global Changes, [ SDE.MCG ] Environmental Sciences/Global Changes, [SDU.STU.CL] Sciences of the Universe [physics]/Earth Sciences/Climatology, [ SDU.STU.CL ] Sciences of the Universe [physics]/Earth Sciences/Climatology, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2009

105. Evaluation of the impact of albedo, orography, SST and large scale conditions on the 2006 West African Monsoon onset

Author: Flaounas, Emmanouil, Bastin, Sophie, Janicot, Serge, SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL)
Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes
Published: 2009

106. A multi-model approach to the Atlantic equatorial mode. Impact on the West African monsoon and tropical teleconnections

Author: Losada, T., Rodriguez-Fonseca, B., Janicot, Serge, Gervois, Sébastien, Chauvin, F., Ruti, P., Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU]Sciences of the Universe [physics]
Abstract: International audience; In the framework of the AMMA-EU project, this work analyses the atmospheric response to the Equatorial mode using a multimodel approach with an ensemble of integrations from 4 AGCMs under a time varying Equatorial SST mode. The Guinean Gulf precipitation, which together with the Sahelian mode accounts for most of the summer West African rainfall variability, is highly coupled to this Equatorial Atlantic SST mode or Atlantic Niño. In a previous study, done with the same models under 1958-97 observed prescribed SSTs, most of the models identify the Equatorial Atlantic SST mode as the one most related to the Guinean Gulf precipitation. The models response to the positive phase of equatorial Atlantic mode (warm SSTs) depicts a direct impact in the equatorial Atlantic, leading to a decrease of the local surface temperature gradient, weakening the West African Monsoon flow and the surface convergence over the Sahel. The results also show a remote influence in both the Pacific and Indian basins; the anomalous southward location of the ITCZ over the Atlantic leads to a global subsidence over the rest of the tropics, weakening the Asian Monsoon and favouring the La Niña conditions in the Pacific.
Published: 2009

107. The role of convectively coupled equatorial Rossby waves in the West African monsoon

Author: Janicot, Serge, Mounier, Flore, Gervois, Sébastien, Sultan, Benjamin, Kiladis, G. N., Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), EQECAT, SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), NOAA Earth System Research Laboratory (ESRL), and National Oceanic and Atmospheric Administration (NOAA)
Subjects: [SDU]Sciences of the Universe [physics]
Abstract: International audience; The intra-seasonal scale variability of rainfall and convection in the African monsoon has been investigated in the recent past years, highlighting the importance of 10-30-day periodicities in rainfall and convective activity over West and Central Africa during the summer. Two independent modes of variability have been detected in the 10-30-day range. One of these two modes, called here the Sahelian mode, is characterized by a westward propagative envelop of convection from eastern Africa to the western tropical Atlantic, associated with a cyclonic circulation ahead of this envelop contributing to enhanced moisture advection and increased convection. In this study we have investigated the relationships between this mode and the occurrence of convectively coupled equatorial Rossby (ER) waves during northern summer. The ER signal has been extracted from the NOAA OLR data by filtering within a box delineated by the dispersion curves of the theoretical ER waves following the Wheeler and Kiladis (1999) techniques. The main EOF mode of the 10-30-day part of this ER signal has been computed and projected onto the unfiltered OLR and atmospheric fields. It displays over sub-Saharan Africa a pattern very similar to the theoretical ER, then demonstrating the occurrence of such wave within the African summer monsoon. This pattern shows a high similarity with the pattern related to the Sahelian mode but also some differences on its southern part. The correlation between the time variation of these two signals is higher than +0.6, meaning that the Sahelian mode can be partly explained by the occurrence of ER waves.
Published: 2009

108. Evaluation of the impact of surface albedo, sea surface temperature and orography in the simulation of the monsoon onset in 2006

Author: Flaounas, Emmanouil, Bastin, Sophie, Janicot, Serge, SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)
Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes
Abstract: The aim of this study is to improve our understanding on the role of the different forcings (oceans, continental surface, large scale activity) on the West African Monsoon (WAM) onset. We thus use a regional model to simulate the WAM circulation of year 2006 so that we can evaluate the model's performance by comparison with observations collected during the Special Observation Period of the AMMA experiment. In particular we bear our attention on the timing of the WAM onset (abrupt displacement of the ITCZ from 5°N to 10°N approximately) and the evaluation of the volume and the location of precipitations. The criterium used to detect the onset is the date when a significant decrease of convection lasting a few days is observed, followed by a northerly displacement of the ITCZ and the associated precipitations. For this purpose, the Weather Research and Forecasting model (WRF) is used to represent the atmospheric circulation over western Africa -with a resolution of 40km, a domain that covers the West and North Africa, the Guinean Gulf, part of the Atlantic ocean (western limit is located at 28.3°W) and of the Mediterranean sea (up to 39°N)-, for a period of seven months (from March to September). In the work presented here, we performed four simulations with a similar configuration of the WRF model but with different albedo, SST and orography values in order to investigate the impact of these elements in the model. Results show that although, the changes done for the sensitivity tests have a striking impact on the WAM dynamics, such as the depth and the seasonal cycle of the Sahelian Heat Low and the Intertropical Discontinuity, the onset date is not subject to any change. The precipitation regime and the ITCZ location are different from one simulation to another but the phase of decreased convection show no temporal flexibility. So, according to this study, albedo and orography are not proved to be key elements to the onset mechanisms. Effects of high SST values in the Guinean Gulf are more important by deranging the ITCZ localization and intensity and furthermore showing a constant rain band over the coastal area at 5°N.
Published: 2009

109. The west African monsoon dynamics. Part III : the quasi-biweekly zonal dipole

Author: Mounier, F., Janicot, Serge, and Kiladis, G. N.
Subjects: Physics::Atmospheric and Oceanic Physics, Physics::Geophysics
Abstract: This paper presents an investigation of the mechanisms giving rise to the main intraseasonal mode of convection in the African monsoon during northern summer, here identified as the quasi-biweekly zonal dipole (QBZD). The QBZD is primarily characterized by a quasi-stationary zonal dipole of convection whose dimension is larger than the West African monsoon domain, with its two poles centered along the Guinean coast and between 30 and 60 W in the equatorial Atlantic. The QBZD dynamical processes within the Atlantic-Africa domain are examined in some detail. The QBZD has a dipole pattern associated with a Walker-type circulation in the near-equatorial zonal plane. It is controlled both by equatorial atmospheric dynamics through a Kelvin wave-like disturbance propagating eastward between its two poles and by land surface processes over Africa, inducing combined fluctuations in surface temperatures, surface pressure, and low-level zonal winds off the coast of West Africa. When convection is at a minimum over central and West Africa, a lack of cloud cover results in higher net shortwave flux at the surface, which increases surface temperatures and lowers surface pressures. This creates an east - west pressure gradient at the latitude of both the ITCZ (10 degrees N) and the Saharan heat low (20 degrees N), leading to an increase in eastward moisture advection inland. The arrival from the Atlantic of the positive pressure signal associated with a Kelvin wave pattern amplifies the low-level westerly wind component and the moisture advection inland, leading to an increase in convective activity over central and West Africa. Then the opposite phase of the dipole develops. Propagation of the QBZD convective envelope and of the associated 200 high-level velocity potential anomalies is detected from the eastern Pacific to the Indian Ocean. When the effect of the Kelvin wave propagation is removed by filtering, the stationary character of the QBZD is highlighted. The impact of the QBZD in combination with a Kelvin wave is illustrated by a case study of the monsoon onset in 1984.
Published: 2008

110. Relationships between climate and year-to-year variability in meningitis outbreaks : a case study in Burkina Faso and Niger - art. no. 34

Author: Yaka, P., Sultan, Benjamin, Broutin, Hélène, Janicot, Serge, Philippon, S., and Fourquet, N.
Subjects: parasitic diseases
Abstract: Background: Every year, West Africa is afflicted with Meningococcal Meningitis (MCM) disease outbreaks. Although the seasonal and spatial patterns of disease cases have been shown to be linked to climate, the mechanisms responsible for these patterns are still not well identified. Results: A statistical analysis of annual incidence of MCM and climatic variables has been performed to highlight the relationships between climate and MCM for two highly afflicted countries: Niger and Burkina Faso. We found that disease resurgence in Niger and in Burkina Faso is likely to be partly controlled by the winter climate through enhanced Harmattan winds. Statistical models based only on climate indexes work well in Niger showing that 25% of the disease variance from year-to-year in this country can be explained by the winter climate but fail to represent accurately the disease dynamics in Burkina Faso. Conclusion: This study is an exploratory attempt to predict meningitis incidence by using only climate information. Although it points out significant statistical results it also stresses the difficulty of relating climate to interannual variability in meningitis outbreaks.
Published: 2008

111. Les impacts agronomiques du climat en Afrique de l'Ouest : une illustration des problèmes majeurs

Author: Sultan, Benjamin, Janicot, Serge, Baron, Christian, Dingkuhn, Michaël, Muller, Bertrand, Traoré, Seydou B., and Sarr, Benoit
Subjects: Changement climatique, Précipitation, Agronomie, P40 - Météorologie et climatologie, Modélisation des cultures, Pauvreté, Impact sur l'environnement, Population rurale, Rendement des cultures, F01 - Culture des plantes, Système d'information, Prévision météorologique
Abstract: Le climat a une influence très forte sur la production agricole, en particulier dans les pays d'Afrique de l'Ouest qui connaissent une grande variabilité climatique et où la pauvreté des populations du Sahel amplifie les impacts des fluctuations du climat. C'est dans ce contexte d'impacts socio-économiques forts auquel s'ajoute la perspective de changement global lié au réchauffement climatique qu'il est apparu essentiel à la communauté scientifique d'orienter ses efforts vers le couplage entre le climat et l'agriculture. Or ce couplage fait ressortir des problèmes majeurs qui sont illustrés et discutés. Ces problèmes concernent : i) les échelles spatiales et temporelles opposant les sciences du climat qui raisonnent sur de grandes échelles permettant d'analyser les dynamiques du climat et les sciences agronomiques qui travaillent à l'échelle locale, la parcelle ou la plante, permettant d'analyser les processus du développement de la culture. ii) les incertitudes des prévisions climatiques et de leurs impacts agronomiques. iii) le transfert de l'information climatique vers les utilisateurs.
Published: 2008

112. Multiscale analysis of precipitable water vapor over Africa from GPS data and ECMWF analyses

Author: Bock, Olivier, Guichard, Françoise, Janicot, Serge, Lafore, Jean-Philippe, Bouin, Marie-Noëlle, Sultan, Benjamin, Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut géographique national [IGN] (IGN), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)
Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], VARIATION SAISONNIERE, BIOCLIMATOLOGIE, Mars, general circulation model, EVAPORATION, GPS.SYSTEME DE POSITIONNEMENT GLOBAL, PRECIPITATION, cardiovascular system, cardiovascular diseases, ANALYSE MULTIVARIABLE, atmospheric dynamics, VARIATION PLURIANNUELLE, circulatory and respiratory physiology
Abstract: 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.
Published: 2007
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113. Climatic and anthropogenic impacts on the variability of water resources : programme, papers, list of participants = Impacts climatiques et anthropiques sur la variabilité des ressources en eau : programme, communications, liste des participants

Author: Janicot, Serge and Mahé, Gil (ed.)
Subjects: VARIATION INTERANNUELLE, TEMPERATURE DE SURFACE, VARIATION SAISONNIERE, PLUIE, ZONE DE CONVERGENCE INTERTROPICALE, CHANGEMENT CLIMATIQUE, INTERACTION OCEAN ATMOSPHERE, MOUSSON D'ETE, EL NINO, MOUSSON D'HIVER
Published: 2007

114. Comparison of ground-based GPS precipitable water vapour to independent observations and NWP model reanalyses over Africa

Author: Bock, Olivier, Bouin, Marie-Noëlle, Walpersdorf, A., Lafore, Jean-Philippe, Janicot, Serge, Guichard, FranÇoise, Agusti-Panareda, Anna, Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL)
Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], NCEP2, ERA-40, AMMA, radiosondes, AERONET
Abstract: This study aims at assessing the consistency between different precipitable water vapour (PWV) datasets over Africa (between 35°N and 10°S). This region is characterized by large spatial and temporal variability of humidity but also by the scarcity of its operational observing network, limiting our knowledge of the hydrological cycle. We intercompare data from observing techniques such as ground-based Global Positioning System (GPS), radiosondes, AERONET sun photometers and SSM/I, as well as reanalyses from European Centre for Medium-Range Weather Forecasts (ERA-40) and National Center for Environmental Prediction (NCEP2). The GPS data, especially, are a new source of PWV observation in this region. PWV estimates from nine ground-based GPS receivers of the international GPS network data are used as a reference dataset to which the others are compared. Good agreement is found between observational techniques, though dry biases of 12-14% are evidenced in radiosonde data at three sites. Reasonable agreement is found between the observational datasets and ERA-40 (NCEP2) reanalyses with maximum bias 9% (14%) and standard deviation 17% (20%). Since GPS data were not assimilated in the ERA-40 and NCEP2 reanalyses, they allow for a fully independent validation of the reanalyses. They highlight limitations in the reanalyses, especially at time-scales from sub-daily to periods of a few days. This work also demonstrates the high potential of GPS PWV estimates over Africa for the analysis of the hydrological cycle, at time-scales ranging between sub-diurnal to seasonal. Such observations can help studying atmospheric processes targeted by the African Monsoon Multidisciplinary Analysis project
Published: 2007
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115. African monsoon multidisciplinary analyses : extended abstracts

Author: Mounier, F., Janicot, Serge, Kiladis, G.N., Genau, I. (ed.), Marsh, S. (ed.), McQuaid, J. (ed.), Redelsperger, J.L. (ed.), Thorncroft, C. (ed.), and Van Den Akker, E. (ed.)
Subjects: ZONE DE CONVERGENCE INTERTROPICALE, ONDE MARINE, INTERACTION OCEAN ATMOSPHERE, MOUSSON D'ETE, ONDE KELVIN, CLIMATOLOGIE
Published: 2006

116. African monsoon multidisciplinary analyses : extended abstracts

Author: Sultan, Benjamin, Drobinski, P., Janicot, Serge, Genau, I. (ed.), Marsh, S. (ed.), McQuaid, J. (ed.), Redelsperger, J.L. (ed.), Thorncroft, C. (ed.), and Van Den Akker, E. (ed.)
Subjects: VENT, ANOMALIE DE TEMPERATURE, CYCLE DIURNE, ANALYSE EN COMPOSANTES PRINCIPALES, MOUSSON D'ETE
Published: 2006

117. African monsoon multidisciplinary analyses : extended abstracts

Author: Correia, S., Sultan, Benjamin, Janicot, Serge, Genau, I. (ed.), Marsh, S. (ed.), McQuaid, J. (ed.), Redelsperger, J.L. (ed.), Thorncroft, C. (ed.), and Van Den Akker, E. (ed.)
Subjects: VARIATION SAISONNIERE, ZONE DE CONVERGENCE INTERTROPICALE, CLIMATOLOGIE, ANALYSE STATISTIQUE
Published: 2006

118. African monsoon multidisciplinary analyses : extended abstracts

Author: Bella-Medjo, M., Janicot, Serge, Sultan, Benjamin, Genau, I. (ed.), Marsh, S. (ed.), McQuaid, J. (ed.), Redelsperger, J.L. (ed.), Thorncroft, C. (ed.), and Van Den Akker, E. (ed.)
Subjects: VENT, ANOMALIE DE TEMPERATURE, CYCLE DIURNE, ANALYSE EN COMPOSANTES PRINCIPALES, MOUSSON D'ETE
Published: 2006

119. African monsoon multidisciplinary analyses : extended abstracts

Author: Sultan, B., Janicot, Serge, Lazar, Alban, Menkès, Christophe, Genau, I. (ed.), Marsh, S. (ed.), McQuaid, J. (ed.), Redelsperger, J.L. (ed.), Thorncroft, C. (ed.), and Van Den Akker, E. (ed.)
Subjects: MODELE, SALINITE, CIRCULATION OCEANIQUE, SIMULATION, INTERACTION OCEAN ATMOSPHERE, MOUSSON D'ETE, TEMPERATURE
Published: 2006

120. Prévision des épidémies de méningite en Afrique Sahélienne à partir de la dynamique atmosphérique

Author: Courel, Marie-Françoise, Fourquet, Nicole, Yaka, Pascal, Philippon, Solenne, Sultan, Benjamin, Janicot, Serge, Legrand, Michel, Chiapello, Isabelle, Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris-Sorbonne (UP4)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École Pratique des Hautes Études (EPHE), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Sorbonne (UP4)-École pratique des hautes études (EPHE)-Institut de Recherche pour le Développement (IRD)-Université Panthéon-Sorbonne (UP1), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])
Subjects: méningite, [SHS.GEO]Humanities and Social Sciences/Geography
Published: 2005

121. A bias-corrected CMIP5 dataset for Africa using CDF-t method. A contribution to agricultural impact studies.

Author: Famien, Adjoua Moise, Janicot, Serge, Ochou, Abe Delfin, Vrac, Mathieu, Defrance, Dimitri, Sultan, Benjamin, and Noël, Thomas
Subjects: *AGRICULTURAL climatology, *CLIMATE change, *AGRICULTURE
Abstract: The objective of this paper is to present a new data set of bias-corrected CMIP5 global climate models (GCMs) daily data over Africa. This dataset was obtained in using the Cumulative Distribution Function Transform (CDF-t) method, a method that has been applied on several regions and contexts but never on Africa. Here CDF-t is used over the period 1950–2099 combining historical runs and climate change scenarios on 6 variables, precipitation, mean near-surface air temperature, near-surface maximum air temperature, near-surface minimum air temperature, surface down-welling shortwave radiation, and wind speed, which are critical variables for agricultural purposes. Evaluation of the results is carried out over West Africa on a list of priority users-based metrics that was discussed and selected with stakeholders and on simulated yield using a crop model simulating maize growth. Bias-corrected GCMs data are compared with another available dataset of bias-corrected GCMs, and the impact of three different reference datasets on bias-corrections is also examined in details. CDF-t is very effective in removing the biases and in reducing the high inter-GCMs scattering. Differences with other bias-corrected GCMs data are mainly due to the differences between the reference datasets. This is particular true for surface down-welling shortwave radiation, which has impacts in terms of simulated maize yields. Projections of future yields over West Africa have quite different levels, depending on bias-correction method used, but they all show a similar relative decreasing trend over the 21st century. [ABSTRACT FROM AUTHOR]
Published: 2017
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122. West African monsoon dynamics and precipitation: the competition between global SST warming and CO increase in CMIP5 idealized simulations.

Author: Gaetani, Marco, Flamant, Cyrille, Bastin, Sophie, Janicot, Serge, Lavaysse, Christophe, Hourdin, Frederic, Braconnot, Pascale, and Bony, Sandrine
Subjects: MONSOONS, METEOROLOGICAL precipitation, CLIMATE change, OCEAN temperature
Abstract: Climate variability associated with the West African monsoon (WAM) has important environmental and socio-economic impacts in the region. However, state-of-the-art climate models still struggle in producing reliable climate predictions. An important cause of this low predictive skill is the sensitivity of climate models to different forcings. In this study, the mechanisms linking the WAM dynamics to the CO forcing are investigated, by comparing the effect of the CO direct radiative effect with its indirect effect mediated by the global sea surface warming. The July-to-September WAM variability is studied in climate simulations extracted from the Coupled Model Intercomparison Project Phase 5 archive, driven by prescribed sea surface temperature (SST). The individual roles of global SST warming and CO atmospheric concentration increase are investigated through idealized experiments simulating a 4 K warmer SST and a quadrupled CO concentration, respectively. Results show opposite and competing responses in the WAM dynamics and precipitation. A dry response (−0.6 mm/day) to the SST warming is simulated in the Sahel, with dryer conditions over western Sahel (−0.8 mm/day). Conversely, the CO increase produces wet conditions (+0.5 mm/day) in the Sahel, with the strongest response over central-eastern Sahel (+0.7 mm/day). The associated responses in the atmospheric dynamics are also analysed, showing that the SST warming affects the Sahelian precipitation through modifications in the global tropical atmospheric dynamics, reducing the importance of the regional drivers, while the CO increase reinforces the coupling between precipitation and regional dynamics. A general agreement in model responses demonstrates the robustness of the identified mechanisms linking the WAM dynamics to the CO direct and indirect forcing, and indicates that these primary mechanisms are captured by climate models. Results also suggest that the spread in future projections may be caused by unbalanced model responses to the CO direct and indirect forcing. [ABSTRACT FROM AUTHOR]
Published: 2017
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123. La variabilité climatique en Afrique de l'Ouest aux échelles saisonnière et intra-saisonnière : II : applications à la sensibilité des rendements agricoles au Sahel

Author: Sultan, Benjamin, Baron, Christian, Dingkuhn, Michaël, Sarr, Benoit, and Janicot, Serge
Subjects: Modèle, Zone agroclimatique, P40 - Météorologie et climatologie, Pluviométrie, F62 - Physiologie végétale - Croissance et développement, Climat de mousson, rendement, F01 - Culture des plantes, Mesure, Pennisetum glaucum, Hydrologie, date de semis, Expérimentation, Agriculture, Variation saisonnière, Climatologie
Abstract: L'agriculture au Sahel, dans la seule région du monde où la production vivrière par habitant diminue, occupe une place très importante dans tous les projets gouvernementaux, et assurer un certain degré de stabilité des rendements des récoltes aux agriculteurs est devenu une priorité nationale pour les institutions de recherche de l'Afrique de l'Ouest. L'eau est un facteur de rendement capital. Pour une gestion optimale des ressources en eau, il est apparu nécessaire de décrire et de comprendre le cycle saisonnier de la mousson au Sahel. A partir d'une étude régionale de la mousson, des événements majeurs ont été identifiés comme marquant la mise en place de la mousson d'une part, et l'occurrence de séquences sèches au coeur de la saison humide, d'autre part. Le but de ce travail est de mesurer l'impact de ces événements à grande échelle sur le rendement à l'échelle locale. Cette première approche pour relier l'échelle climatique régionale et la parcelle a été menée au moyen d'expériences de sensibilité sur un modèle agronomique SARRAH (Système d'analyse régionale de risques agroclimatiques) qui simule la réponse du rendement à la contrainte hydrique. Ces expériences visent à mesurer la sensibilité du rende-ment potentiel (limité par le climat mais non par les ressources minérales) à la date de semis pour la culture du mil à Niamey sur la période 1968-1990. La variabilité du rendement potentiel au sein des différentes simulations est discutée pour tenter d'extraire les différentes causes de cette variabilité: validité du critère de décision pour le choix de la date de semis, rôle de la variabilité interannuelle, et impact des épisodes secs au coeur de la saison humide. On montre alors l'apport de l'étude régionale de la mousson pour améliorer le rendement agricole à l'échelle de la parcelle.
Published: 2005

124. Climate Drives the Meningitis Epidemics Onset in West Africa

Author: Sultan, Benjamin, Labadi, Karima, Guégan, Jean-François, and Janicot, Serge
Subjects: Air Movements, Infectious Diseases, Atmosphere, Africa, Seasons, Meningitis, Meningococcal, Communicable Diseases, Research Article, Disease Outbreaks
Abstract: Background Every year West African countries within the Sahelo-Sudanian band are afflicted with major meningococcal meningitis (MCM) disease outbreaks, which affect up to 200,000 people, mainly young children, in one of the world's poorest regions. The timing of the epidemic year, which starts in February and ends in late May, and the spatial distribution of disease cases throughout the “Meningitis Belt” strongly indicate a close linkage between the life cycle of the causative agent of MCM and climate variability. However, mechanisms responsible for the observed patterns are still not clearly identified. Methods and Findings By comparing the information on cases and deaths of MCM from World Health Organization weekly reports with atmospheric datasets, we quantified the relationship between the seasonal occurrence of MCM in Mali, a West African country, and large-scale atmospheric circulation. Regional atmospheric indexes based on surface wind speed show a clear link between population dynamics of the disease and climate: the onset of epidemics and the winter maximum defined by the atmospheric index share the same mean week (sixth week of the year; standard deviation, 2 wk) and are highly correlated. Conclusions This study is the first that provides a clear, quantitative demonstration of the connections that exist between MCM epidemics and regional climate variability in Africa. Moreover, this statistically robust explanation of the MCM dynamics enables the development of an Early Warning Index for meningitis epidemic onset in West Africa. The development of such an index will undoubtedly help nationwide and international public health institutions and policy makers to better control MCM disease within the so-called westward–eastward pan-African Meningitis Belt., An analysis of winds and yearly meningitis epidemics in West Africa shows a surprisingly close correlation that could help to predict disease outbreaks
Published: 2005

125. Climate drives the meningitis onset in West Africa

Author: Sultan, Benjamin, Labadi, Karima, Guégan, Jean-François, Janicot, Serge, Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris-Sorbonne (UP4)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Génétique et évolution des maladies infectieuses (GEMI), Centre National de la Recherche Scientifique (CNRS)-Université Montpellier 1 (UM1)-Institut de Recherche pour le Développement (IRD [France-Sud]), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École Pratique des Hautes Études (EPHE), Université Montpellier 1 (UM1)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL)
Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2005
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126. Turbulent Air-Sea Fluxes from Satellites and Models in the Equatorial Atlantic

Author: Bourras, Denis, Caniaux, G., Mbengue, A.-A., Janicot, Serge, De Coëtlogon, Gaëlle, Diongue Niang, A., Eymard, Laurence, André, C., Karbou, F., Cardon, Catherine, Centre d'étude des environnements terrestre et planétaires (CETP), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment
Published: 2005

127. La variabilité climatique en Afrique de l'Ouest aux échelles intra-saisonnières. 1ère partie : Analyse diagnostique de la mise en place de la mousson et de la variabilité intra-saisonnière de la convection

Author: Sultan, Benjamin, Janicot, Serge, Laboratoire d'océanographie dynamique et de climatologie (LODYC), and Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]
Published: 2004

128. Agricultural impacts of regional variability of the West African monsoon

Author: Sultan, Benjamin, Baron, Christian, Dingkuhn, Michaël, and Janicot, Serge
Subjects: date de semis, P40 - Météorologie et climatologie, Modèle de simulation, Variation saisonnière, Rendement des cultures, F01 - Culture des plantes, Prévision météorologique
Abstract: Agriculture in the Sudano-Sahelian zone is heavily dependent on the seasonal characteristics of rainfall, i.e. onset, length and termination of the wet season, seasonal rainfall totals and intraseasonal rainfall distribution. This study seeks to characterize components of regional climatic variability and their impact on simulated, attainable, plot-level yields of millet. First, we will characterize at a regional scale two main events in the seasonal pattern of the monsoon over West Africa by using a daily rainfall dataset over the 1968-1990 period, that is, (1) the "onset" of the summer monsoon characterized by an abrupt northward shift of the ITCZ from 5°N to 10°N around the 24th June, and (2) large and coherent, intra-seasonal rainfall fluctuations at two different spectral windows, between 10 and 25 days and between 25 and 60 days. Second, we will investigate the impact of these regional phenomena on local crop yields using SARRAH, a crop model simulating water-limited yield, by means of sensitivity analyses. The response of attainable yield (limited by climate and water resources but not mineral nutrition) to sowing date was studied for 19 years of the 1968-1990 period for a 90-day millet crop at Niamey. Yield variability is analysed with respect to the apparent validity of regional (climatic) and local (rainfall events) decision criteria for sowing date, while taking into consideration interannual variability of rainfall and intra-seasonal dry spells. Results indicate that information on regional climate dynamics might help improve crop production locally.
Published: 2004

129. L'épidémie de méningite au Mali et la circulation atmosphérique en Afrique de l'Ouest

Author: Sultan, Benjamin, Labadi, Karima, Beltrando, G., Janicot, Serge, Laboratoire d'océanographie dynamique et de climatologie (LODYC), and Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]
Published: 2004

130. L'épidémie de Méningite au Mali et la circulation atmosphérique à grande échelle en Afrique de l'Ouest

Author: Sultan, Benjamin, Labadi, K., Beltrando, Gérard, Janicot, Serge, Laboratoire d'océanographie dynamique et de climatologie (LODYC), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris-Sorbonne (UP4)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École Pratique des Hautes Études (EPHE)
Subjects: Afrique de l'Ouest, Circulation atmosphérique, Epidémie, [SHS.GEO]Humanities and Social Sciences/Geography, Mali, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2004

131. The West African monsoon dynamics, Part I : Intra-seasonal variability

Author: Sultan, Benjamin, Janicot, Serge, Diedhiou, Arona, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]
Abstract: Intraseasonal variability in the West African monsoon is documented by using daily gridded datasets of rainfall and convection, and reanalyzed atmospheric fields, over the period 1968-90. Rainfall and convection over West Africa are significantly modulated at two intraseasonal timescales, 10-25 and 25-60 day, leading to variations of more than 30% of the seasonal signal. A composite analysis based on the dates of the maximum (minimum) of a regional rainfall index in wet (dry) sequences shows that these sequences last, on average, 9 days and belong to a main quasiperiodic signal of about 15 days. A secondary periodicity of 38 days is present but leads to a weaker modulation. During a wet (dry) sequence, convection in the ITCZ is enhanced (weakened) and its northern boundary moves to the north (south), while the speed of the African easterly jet decreases (increases), the speed of the tropical easterly jet increases (decreases), and the monsoon flow becomes stronger (weaker), all these features being similar to the ones associated with interannual variability characterizing wet and dry years. This modulation of convection at intraseasonal timescales is not limited to West Africa but corresponds to a westward-propagating signal from eastern Africa to the western tropical Atlantic. An enhanced monsoon phase is associated with stronger cyclonic activity in the low levels over the Sahel associated with stronger moisture advection over West Africa. Five days before the full development of the wet phase, a stronger cyclonic circulation at 20ЊE induces enhanced southerly winds along 25ЊE where convection enhances, while another westwardpropagating cyclonic circulation is located at 0Њ. This atmospheric pattern is linked to the enhancement of the subsiding branch of the northern Hadley cell at 35ЊN, northerly advection of drier air over West Africa, and to increased dry convection in the heat low at 20ЊN. It propagates westward, leading to a zonally extended area of enhanced monsoon winds over West Africa consistent with the occurrence of the wet phase.
Published: 2003
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132. AMMA's contribution to the evolution of prediction and decision-making systems for West Africa

Author: Polcher, Jan, Parker, Douglas J., Gaye, Amadou, Diedhiou, Arona, Eymard, Laurence, Fierli, Federico, Genesio, Lorenzo, Hoeller, Hartmut, Janicot, Serge, Lafore, Jean-Philippe, Karambiri, Harouna, Lebel, Thierry, Redelsperger, Jean-Luc, Reeves, Claire E., Ruti, Paolo, Sandholt, Inge, Thorncroft, Chris, Polcher, Jan, Parker, Douglas J., Gaye, Amadou, Diedhiou, Arona, Eymard, Laurence, Fierli, Federico, Genesio, Lorenzo, Hoeller, Hartmut, Janicot, Serge, Lafore, Jean-Philippe, Karambiri, Harouna, Lebel, Thierry, Redelsperger, Jean-Luc, Reeves, Claire E., Ruti, Paolo, Sandholt, Inge, and Thorncroft, Chris
Published: 2011

133. Climate & agriculture in West Africa: Benjamin Sultan and Serge Janicot explain how climate impacts relate to agriculture throughout West Africa

Author: Sultan, Benjamin and Janicot, Serge
Subjects: Agricultural industry, Aerospace and defense industries, Business, Business, international, Electronics and electrical industries, Geography
Abstract: Climate has a strong influence on agricultural production, considered as the most weather-dependent of all human activities, with socio-economical impacts whose severity varies from one region to another. [FIGURE 1 [...]
Published: 2006

134. Atmospheric response to sea‐surface temperature in the eastern equatorial Atlantic at quasi‐biweekly time‐scales

Author: de Coëtlogon, Gaëlle, primary, Leduc‐Leballeur, Marion, additional, Meynadier, Rémi, additional, Bastin, Sophie, additional, Diakhaté, Moussa, additional, Eymard, Laurence, additional, Giordani, Hervé, additional, Janicot, Serge, additional, and Lazar, Alban, additional
Published: 2013
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135. Recent changes in air temperature, heat waves occurrences, and atmospheric circulation in Northern Africa

Author: Fontaine, Bernard, primary, Janicot, Serge, additional, and Monerie, Paul-Arthur, additional
Published: 2013
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136. Increased CO2outgassing in February-May 2010 in the tropical Atlantic following the 2009 Pacific El Niño

Author: Lefèvre, Nathalie, primary, Caniaux, Guy, additional, Janicot, Serge, additional, and Gueye, Abdou Karim, additional
Published: 2013
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137. Seasonal influence of the sea surface temperature on the low atmospheric circulation and precipitation in the eastern equatorial Atlantic.

Author: Meynadier, Rémi, Coëtlogon, Gaëlle, Leduc-Leballeur, Marion, Eymard, Laurence, and Janicot, Serge
Subjects: ATMOSPHERIC circulation, ATMOSPHERIC physics, OCEAN temperature, METEOROLOGICAL precipitation
Abstract: The air-sea interaction in the Gulf of Guinea and its role in setting precipitation at the Guinean coast is investigated in the present paper. This study is based on satellite observations and WRF simulations forced by different sea surface temperature (SST) patterns. It shows that the seasonal cold tongue setup in the Gulf of Guinea, along with its very active northern front, tends to strongly constrain the low level atmospheric dynamics between the equator and the Guinean coast. Underlying mechanisms including local SST effect on the marine boundary layer stability and hydrostatically-changed meridional pressure gradient through changes in SST gradient are quantified in WRF regarding observations and CFSR reanalyses. Theses mechanisms strongly impact moisture flux convergence near the coast, leading to the installation of the first rainy season of the West African Monsoon (WAM) system. The current study details the mechanisms by which the Atlantic Equatorial cold tongue plays a major role in the pre-onset of the boreal WAM. [ABSTRACT FROM AUTHOR]
Published: 2016
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138. État des recherches sur l’attribution de la variabilité décennale récente en Afrique de l’Ouest

Author: Janicot, Serge, primary
Published: 2012
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139. La mousson ouest-africaine : introduction à quelques contributions du programme d'étude multidisciplinaire AMMA

Author: Janicot, Serge, primary, Redelsperger, Jean-Luc, additional, and Lebel, Thierry, additional
Published: 2012
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140. Évolution de notre compréhension du système de mousson ouest-africain

Author: Lafore, Jean-Philippe, primary, Asencio, Nicole, additional, Bouniol, Dominique, additional, Couvreux, Fleur, additional, Flamant, Cyrille, additional, Guichard, Françoise, additional, Hall, Nicholas, additional, Janicot, Serge, additional, Kocha, Cécile, additional, Lavaysse, Christophe, additional, Leroux, Stéphanie, additional, Poan, Emmanuel, additional, Peyrillé, Philippe, additional, Roca, Rémy, additional, Roehrig, Romain, additional, Roux, Frank, additional, and Saïd, Frédérique, additional
Published: 2012
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141. Variabilité pluviométrique, changement climatique et régionalisation en région de mousson africaine

Author: Fontaine, Bernard, primary, Roucou, Pascal, additional, Camara, Moctar, additional, Vigaud, Nicolas, additional, Konaré, Abdourahamane, additional, Sanda, Seidou Ibrah, additional, Diedhiou, Arona, additional, and Janicot, Serge, additional
Published: 2012
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142. Les avancées d'AMMA sur les interactions océan-atmosphère

Author: Caniaux, Guy, primary, Giordani, Hervé, additional, Redelsperger, Jean-Luc, additional, Wade, Malick, additional, Bourlès, Bernard, additional, Bourras, Denis, additional, Coëtlogon, Gaëlle de, additional, Penhoat, Yves du, additional, Janicot, Serge, additional, Key, Erica, additional, Koffi, Urbain, additional, Kolodziejczyk, Nicolas, additional, Eymard, Laurence, additional, Jouanno, Julien, additional, Lazar, Alban, additional, Leduc-Leballeur, Marion, additional, Lefèvre, Nathalie, additional, Marin, Frédéric, additional, Nguyen, Hanh, additional, and Parard, Gaëlle, additional
Published: 2012
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143. The West African monsoon onset in 2006: sensitivity to surface albedo, orography, SST and synoptic scale dry-air intrusions using WRF

Author: Flaounas, Emmanouil, primary, Janicot, Serge, additional, Bastin, Sophie, additional, and Roca, Rémy, additional
Published: 2011
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144. Impact of the Indian part of the summer MJO on West Africa using nudged climate simulations

Author: Mohino, Elsa, primary, Janicot, Serge, additional, Douville, Hervé, additional, and Li, Laurent Z. X., additional
Published: 2011
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145. The role of the Indian monsoon onset in the West African monsoon onset: observations and AGCM nudged simulations

Author: Flaounas, Emmanouil, primary, Janicot, Serge, additional, Bastin, Sophie, additional, Roca, Rémy, additional, and Mohino, Elsa, additional
Published: 2011
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146. Large-scale circulation patterns and related rainfall in the Amazon Basin: a neuronal networks approach

Author: Espinoza, Jhan Carlo, primary, Lengaigne, Matthieu, additional, Ronchail, Josyane, additional, and Janicot, Serge, additional
Published: 2011
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147. Interannual and decadal SST‐forced responses of the West African monsoon

Author: Rodríguez‐Fonseca, Belén, primary, Janicot, Serge, additional, Mohino, Elsa, additional, Losada, Teresa, additional, Bader, Juergen, additional, Caminade, Cyril, additional, Chauvin, Fabrice, additional, Fontaine, Bernard, additional, García‐Serrano, Javier, additional, Gervois, Sebastien, additional, Joly, Mathieu, additional, Polo, Irene, additional, Ruti, Paolo, additional, Roucou, Pascal, additional, and Voldoire, Aurore, additional
Published: 2011
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148. AMMA's contribution to the evolution of prediction and decision-making systems for West Africa

Author: Polcher, Jan, primary, Parker, Douglas J., additional, Gaye, Amadou, additional, Diedhiou, Arona, additional, Eymard, Laurence, additional, Fierli, Federico, additional, Genesio, Lorenzo, additional, Höller, Hartmut, additional, Janicot, Serge, additional, Lafore, Jean-Philippe, additional, Karambiri, Harouna, additional, Lebel, Thierry, additional, Redelsperger, Jean-Luc, additional, Reeves, Claire E., additional, Ruti, Paolo, additional, Sandholt, Inge, additional, and Thorncroft, Chris, additional
Published: 2011
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149. Sahel rainfall and decadal to multi-decadal sea surface temperature variability

Author: Mohino, Elsa, primary, Janicot, Serge, additional, and Bader, Juergen, additional
Published: 2010
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150. Regional climate modelling of the 2006 West African monsoon: sensitivity to convection and planetary boundary layer parameterisation using WRF

Author: Flaounas, Emmanouil, primary, Bastin, Sophie, additional, and Janicot, Serge, additional
Published: 2010
Full Text: View/download PDF

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