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Publications (196)
The tropical cloud forest ecosystem in Western Equatorial Africa (WEA) is known to be sensitive to the presence of an extensive and persistent low-level stratiform cloud deck during the long dry season from June to September (JJAS). Here we present a new climatology of the diurnal cycle of the low-level cloud cover from surface synoptic stations ov...
Within the equatorial zone, Western Equatorial Africa (WEA) has a record low sunshine duration during the June–September dry season due to the persistence of low clouds. This study examines the ability of two reanalysis products (ERA5 and MERRA-2) and eight CMIP6 models (both coupled and atmosphere-only historical simulations) to reproduce the clim...
Drought is a meteorological and hydrological phenomenon affecting the environment, agriculture, and socioeconomic conditions, especially in arid and semi-arid regions. A better understanding of drought characteristics over short and long timescales is therefore crucial for drought mitigation and long-term strategies. For the first time, this study...
This talk presents preliminary results of the DYVALOCCA program about the space-time variability of the low-level cloud cover over western equatorial Africa.
Malgré son importance bioclimatique, peu d'études se sont intéressées à la couverture nuageuse basse stratiforme de saison sèche (juin-septembre) de la façade Atlantique de l'Afrique Centrale. Grâce à des données in-situ documentant la période 1971-2019, nous montrons que cette couverture nuageuse est sous-estimée par les observations satellites SA...
Western Equatorial Africa is one of the least sunny areas in the world. Yet, this has attracted little research so far. As in many other parts of Africa, light availability is mainly estimated using in-situ measurements of sunshine duration (SDU). Therefore this study conducts the first characterization of SDU evolution during the annual cycle for...
Western Equatorial Africa (WEA) has a record low sunshine duration during the June–September dry season due to the persistence of low clouds. This study examines the ability of two reanalysis products (ERA5 and MERRA-2) and 8 CMIP6 models (both coupled and atmosphere-only historical simulations) to reproduce the climatology of these low clouds, by...
For the first time the spatial and temporal variability of rainfall in the Republic of Djibouti is investigated using data from 14 weather stations over the period 1946–2017. Due to limited data availability, high‐resolution long‐term satellite rainfall products (CHIRPS, PERSIANN‐CDR, TAMSATv3, ARC2) and ERA5 reanalysis also contribute to document...
The southern coastal belt of West Africa (SCWA) with its high population density and many major cities, combined to the low elevation and poor urban planning, is very vulnerable to floods resulting from extreme rainfall events. The aim of this paper is to analyze the characteristics of extreme rainfall in the SCWA during the 1981-2015 period, in te...
This study interprets 11 years (2006 to 2016) and 6 months (March to August in 2017) of respectively monthly and daily isotopic (δD and δ18O) monitoring of rain at Douala (Cameroon), a humid tropical station in Western Africa. The main scope is to analyze the climate controls on precipitation isotopes at different timescales. Firstly, we examine th...
This study characterizes the future changes in extreme rainfall and air temperature in the Mono river basin where the main economic activity is weather dependent and local populations are highly vulnerable to natural hazards, including flood inundations. Daily precipitation and temperature from observational datasets and Regional Climate Models (RC...
Daily rainfall in southern West Africa (4–8° N, 7° W–3° E) is analyzed with the aim of documenting the intense rainfall events which occur in coastal Ivory Coast, Ghana, Togo, and Benin. The daily 99th percentile (P99) shows that the coastline experiences higher intensity rainfall than inland areas. Using Tropical Rainfall Measuring Mission (TRMM)...
Near real-time precipitation is essential to many applications. In Africa, the lack of dense rain-gauge networks and ground weather radars makes the use of satellite precipitation products unavoidable. Despite major progresses in estimating precipitation rate from remote sensing measurements over the past decades, satellite precipitation products s...
Dry spells are natural hazards which have strong impacts on the environment and on many socioeconomic sectors. Their evolution in the Mediterranean Basin is a major issue because it is one of the most extreme hot spots of climate change world-wide. Very long dry spells are defined as climatic events characterized by their location, spatial extent,...
The modulation of the rainfall diurnal cycle at intraseasonal and interannual timescales is examined using gridded rainfall data over Eastern Africa and the nearby Indian Ocean for the period 1998-2014. Our focus is on the October-December season which is strongly impacted by both the Madden-Julian Oscillation (MJO) and the Indian Ocean Dipole Mode...
An intercomparison of seven gridded rainfall products incorporating satellite data (ARC, CHIRPS, CMORPH, PERSIANN, TAPEER, TARCAT, TMPA) is carried out over Central Africa, by evaluating them against three observed datasets: (i) the WaTFor database, consisting of 293 (monthly records) and 154 (daily records) rain gauge stations collected from globa...
Rainfall thresholds under which forests grow in Central Africa are lower than those of Amazonia and SE Asia. Attention is thus regularly paid to rainfall whose seasonality and interannual variability has been shown to control Central African forests' water balance and photosynthetic activity. Nonetheless, light availability is also recognized as a...
The book chapter describes the mean climate and seasonal cycle of the West African monsoon in French. It is a translation from the Englisch version of the book published by Wiley
Ce travail porte sur l’étude des longues séquences hivernales sans pluie à l’échelle de l’ensemble du bassin méditerranéen. L’objectif est de définir ces évènements climatiques « extrêmes » comme des objets géographiques et climatiques caractérisés par une localisation, une extension spatiale et temporelle, puis d’en mesurer les impacts sur la prod...
Les conditions d'éclairement prévalant en Afrique Centrale et leur impact potentiel sur les traits et le fonctionnement des forêts ont été peu étudiés. S'appuyant sur des estimations satellitaires horaires de rayonnement solaire incident, et tenant compte des interactions d'échelles entre cycle diurne et cycle saisonnier, nous montrons que le Gabon...
Ce travail porte sur l’étude des longues séquences hivernales sans pluie à l’échelle de l’ensemble du bassin méditerranéen. L’objectif est de définir ces événements climatiques « extrêmes » comme des objets géographiques et climatiques caractérisés par une localisation, une extension spatiale et temporelle, puis d’en mesurer les impacts sur la prod...
Very long dry spell events occurring during win-ter are natural hazards to which the Mediterranean region is extremely vulnerable, because they can lead numerous impacts for environment and society. Four dry spell pat-terns have been identified in a previous work. Identifying the main associated atmospheric conditions controlling the dry spell patte...
Exceptional dry spells, in this study referred to as very long dry spells (VLDS), are natural hazards to which the Mediterranean region is extremely vulnerable, with socio-economic and environmental impacts. In this study, they are characterized in terms of location, spatial extent, duration, temporal variability and associated atmospheric circulat...
The relationships between precipitation and temperature in the central sudano-sahelian belt are investigated by analyzing 50 years (1959-2008) of observed temperature (Tx and Tn) and rainfall variations. At daily timescale , both Tx and Tn show a marked decrease as a response to rainfall occurrence, with a strongest departure from normal one day af...
Apple tree bloom onset in Germany has advanced by 2 days/decade in 1951-2014 and by 3 days/decade in 1988-2014, behaving similarly in respect to its evolution since 1951 and its sensitivity to temperature to other species' phenological spring phases. The evolution however was not linear; by conducting a split moving-window dissimilarity analysis (S...
Apple tree bloom onset in Germany has advanced by 2 days/decade in 1951-2014 and by 3 days/decade in 1988-2014, behaving similarly in respect to its evolution since 1951 and its sensitivity to temperature to other species' phenological spring phases. The evolution however was not linear; by conducting a split moving-window dissimilarity analysis (S...
Apple tree bloom onset in Germany has advanced by 2 days/decade in 1951-2014 and by 3 days/decade in 1988-2014, behaving similarly in respect to its evolution since 1951 and its sensitivity to temperature to other species' phenological spring phases. The evolution however was not linear; by conducting a split moving-window dissimilarity analysis (S...
Many African countries whose economies are largely based on weather/climate sensitive sectors are vulnerable to long-term changes in weather and climate. This study is aimed at assessing whether the recent decades have observed any significant trend in the intraseasonal descriptors (ISDs) of wet and dry spells at local and sub-regional levels at se...
Mean diurnal rainfall regimes over Eastern Africa (also referred to as the Greater Horn of Africa) are studied based on 3-hourly data from the TRMM 3B42 data set, averaged over a 17-year period (1998–2014). The consistency with long-term mean raingauge data, available for partly independent periods, varies from good (Sudan, Ethiopia, Eritrea and So...
Relationships between daily precipitation and daily maximum and minimum temperature (Tx and Tn, respectively) are analyzed at station level over the Greater Horn of Africa (GHA). Rainfall occurrence is associated with either above normal Tn (mostly in cool highland areas) or below normal Tn (especially lowland, hot environments and early parts of t...
Climate change of Benin for the period 1950-2010 and its impact on surface water. In West Africa
and Benin in particular, variability / climate change affects the availability of surface water resources. Thus,
this study aims to analyze the rainfall field of Benin from the fifty three (53) meteorological stations from 1950
to 2010 and to detect the...
Les précipitations hivernales en méditerranée (septembre à avril) sont essentielles pour la ressource en eau, l’humidité des sols, la végétation ou encore l’agriculture. Une baisse des précipitations durant cette saison pourrait causer d’importants impacts tant sur un aspect économique que social. Dans cette étude, la variabilité des épisodes de sé...
Ce travail fait un état des lieux de la qualité temporelle et de la densité spatiale des séries pluviométriques du Cameroun, Gabon, Congo, RCA et RDC, en particulier sur la période récente (1973-2014) grâce à la base de données internationale GSOD. Face aux énormes lacunes observées, ces résultats vont permettre d'orienter les choix métrologiques e...
The E-OBS precipitation gridded data set v.10.0 is used to detect Very Long Dry Spell (VLDS) events over the entire Mediterranean Basin for the 1957-2013 period, during the wet season (September to April). The main objective is to characterize these events as climatic objects, in terms of location, spatial extent, duration and temporal variability....
This paper documents the capability of the ARW/WRF regional climate model to regionalize near-surface atmospheric variables at high resolution (8 km) over Burgundy (northeastern France) from daily to interannual timescales. To that purpose, a 20-year continuous simulation (1989–2008) was carried out. The WRF model driven by ERA-Interim reanalyses w...
The E-OBS precipitation gridded data set v.10.0 is used to detect Very Long Dry Spell (VLDS) events over the entire Mediterranean Basin for the 1957-2013 period, during the wet season (September to April). The main objective is to characterize these events as climatic objects, in terms of location, spatial extent, duration and temporal variability....
The E-OBS precipitation gridded data set v.10.0 is used to detect Very Long Dry Spell (VLDS) events over the entire Mediterranean Basin for the 1957-2013 period, during the wet season (September to April). The main objective is to characterize these events as climatic objects, in terms of location, spatial extent, duration and temporal variability....
The reconstruction of daily rainfall data at the station scale can be necessary to study the climate change or other applied climatology work. This is the case in tropical area to analyze rainy season characteristics (onset and cessation dates, duration, etc.). A classical methodological approach based on multiple linear stepwise regression is appl...
The main objective of this study is to characterize Mediterranean rainfall spatiotemporal features from 1950 to 2013, with a focus on intense events. Results show a general decrease in precipitation amounts during the September to April period. The Mediterranean Basin also shows a strong decrease in the number of rainy days in northern Portugal, Al...
L’objectif de cette étude est d’appréhender les caractéristiques spatio-temporelles des phénomènes pluviométriques à l’échelle du bassin méditerranéen de 1950 à 2013 et notamment des évènements intenses. Les résultats montrent une baisse du cumul de pluie, durant la période de septembre à avril, quasi-généralisée à l’ensemble du bassin méditerranée...
The Mediterranean basin has quite a unique character that results both from physiographic and climatic conditions and historical and societal developments. Because of the latitudes it covers, the Mediterranean basin is a transition area under the influence of both mid-latitudes and tropical variability. Because in such transition area, the Mediterr...
Les peuplements de Douglas (Pseudotsuga menziesii) en Bourgogne ont été lourdement affectés depuis l’épisode de sécheresse-canicule de 2003. Leur vulnérabilité au climat est attribuable à l'amplitude et au cumul des contraintes hydriques qui s'exercent durant un cycle de végétation (Sergent et al, 2012). Dans le but d'affiner le diagnostic et dans...
Two rainy seasons are recognized over Kenya. These are the long rainy season March to May (MAM) and the short rainy season of October to December (OND). During these seasons the whole country experiences rainfall. However, over the central Rift Valley, the second rainfall season seems to be missing. This is due to the escarpments over the region wi...
Mediterranean winter precipitations (September to April) are important for annual water resources, summer ground moisture, vegetation and agriculture. Decrease of precipitation during this season may cause many important economic and social impacts. Winter dry spells variability in the Mediterranean Basin are analysed in this study. E-obs Data grid...
Le bassin méditerranéen est affecté de façon répétitive par des épisodes de précipitations intenses aux forts impacts socio-économiques et environnementaux. Cette étude propose de repérer des configurations spatiales récurrentes des précipitations intenses quotidiennes (CRPI) à l’échelle de l’ensemble du bassin méditerranéen, et de déterminer les f...
Résumé - 6 régimes de pluie redondants et récurrents sont observés sur le bassin Méditerranéen pour la période 1979-2013 : 5 sont associés à des excédents pluvieux régionaux (sud-ouest méditerranéen, centre-nord méditerranéen, est méditerranéen, ouest méditerranéen et nord-ouest méditerranéen) et 1 à un déficit généralisé. Chacun de ces régimes plu...
Global carbon, water and energy cycles are substantially driven by vegetation phenology. In particular tropical rainforests have been shown to be a key component of the climate system as they act as major water vapor sources and carbon dioxide sink. For these reasons their evolution in response to both human pressure and climate change is critical....
Mount Kenya is an equatorial mountain whose climatic setting is fairly simple (two rainy seasons in
March–May, the Long Rains, andOctober–December, the Short Rains) though concealing significant spatial variations related
to elevation and aspect (part I, Camberlin et al., 2014). This part II is dedicated to the sensitivity of sorghum yields to clim...
Accurate seasonal predictions of rainfall may reduce climatic risks that farmers are usually faced with across the tropical and subtropical zones. However, although regional-scale seasonal amounts have regularly been forecasted since 1997/98, the practical use of these seasonal predictions is still limited by myriad factors. This paper synthesizes...
La reconstitution de données de pluies manquantes au pas de temps quotidien et à l'échelle stationnelle est parfois nécessaire pour l'étude de changements climatiques ou des travaux de climatologie appliquée. C'est le cas, en domaine tropical, de l'analyse des variations des caractéristiques des saisons des pluies (dates de démarrage et de fin, dur...
L'objectif de cette étude est d'analyser la dynamique hydrométéorologique du bassin et la distribution des crues entrantes au barrage de Nangbéto afin d'apprécier les risques d'inondation dans la basse vallée du fleuve. Les données utilisées sont : les débits journaliers du Mono (m3.s-1) à Nangbéto et à Athiémé, l'évapotranspiration (mm/jour, calcu...
