Search results for "WES"
showing 10 items of 1585 documents
Recent changes in measured wind in the NE Atlantic and variability of correlation with NAO
2010
The paper deals with wind measurements, recorded since the 1950s, at twelve meteorological stations along a transect near the westernmost European border, between 64° and 44° N. Extreme wind speed tends to decrease sharply near the northern boundary (at Reykjavick), near the middle of the study area (at Shannon and Valentia) and near the southern boundary (at Brest and Cap Ferret), to increase at Thorshavn, with less significant trends at the other stations. Average wind speeds confirm the above tendencies, with an additional increasing speed at Lerwick, Kirkwall, Malin Head, Belle-Ile and Cap Ferret. To compare changes in wind activity, the data have been subdivided into three periods: unt…
Global atmospheric response to specific linear combinations of the main SST modes. Part I: numerical experiments and preliminary results
1996
Abstract. This article investigates through numerical experiments the controversial question of the impact of El Niño-Southern Oscillation (ENSO) phenomena on climate according to large-scale and regional-scale interhemispheric thermal contrast. Eight experiments (two considering only inversed Atlantic thermal anomalies and six combining ENSO warm phase with large-scale interhemispheric contrast and Atlantic anomaly patterns) were performed with the Météo-France atmospheric general circulation model. The definition of boundary conditions from observed composites and principal components is presented and preliminary results concerning the month of August, especially over West Africa and the …
Du contrat dans le western, de Ford à Eastwood, de My Darling Clementine (1946) à Unforgiven (1992)
2013
International audience
City gates of Augustodunum and their architectural models (Gaul, Italy, Western Provinces of the Roman Empire)
2013
Augustodunum, civitas Aeduorum, roman city founded under the reign of Augustus, was equipped with four roman city gates : the gate of Arroux and the gate of Saint André, both well preserved, the gate of Saint Andoche which sole remaining part is a flanking tower, and the gate of Rome, destroyed long ago.The heart of this study lies in the stratigraphic reading of those gates structure and in thoughts about the building site of Autun’s city gates operating process. Moreover, since the 16th century, antiquaries, travelers and artists have described in many ways their visits to the roman city gates of Autun. These accounts constitute a major documentary collection of written and iconographical…
How could hydro-climatic conditions evolve in the long term in West Africa? The case study of the Bani River catchment
2011
International audience; This paper assesses the future variability of water resources in the long term over a large Sudano- Sahelian catchment in West Africa. Flow simulations were performed with a daily conceptual model. The climate models HadCM3 and MPI-M (based on SRES-A2) were used to provide future climate scenarios over the catchment. Outputs from these models were used to generate daily rainfall and temperature series for the 21st century according to: (i) application of the unbias and delta methods, and (ii) spatial and temporal downscaling. A temperature-based formula was used to calculate present and future potential evapotranspiration (PE). The daily rainfall and PE series were i…
Dissolved silica in the Garonne River waters : changes in the weathering dynamics
2000
The major ion chemistry of the Garonne River is indicative of seasonal variations in the weathering dynamics of the drainage basin. Using the geochemical model MEGA for calculation of the contribution of atmospheric CO2 to the total bicarbonate fluxes exported by the Garonne River allows estimations of the concentrations of the major dissolved elements that originate from silicate- and carbonate-rock weathering. The molecular ratio SiO2/Al2O3 was calculated for the 1989–1992 period to identify the main type of weathering in the Garonne River, and montmorillonite was shown to be the major mineral occurring in the weathering products. The seasonal variations of the SiO2/Al2O3 ratio also showe…
Variabilité intra-saisonnière et multi-décennale de la téléconnexion entre les pressions de surface (100°W–50°E ; 30°–70°N) et les ENSO/LNSO (1873–19…
2000
Abstract The relationships between an index of the NINO3.4 region and the wintertime sea level pressure (hereafter SLP) anomalies on the extratropical North Atlantic and the bordering areas (100°W–50°E; 30°–70°N) are studied for 1873–1996. This study emphasizes the need of a careful pooling of months and the multi-decadal variability of the ENSO/LNSO influence on the extratropical North Atlantic. We calculate the mean monthly climate anomalies for the 20 warmest and the 20 coldest NINO3.4 (170°–120°W; 5°N–5°S) years from October to March. The composite of SLP anomalies for the 20 warmest NINO3.4 years shows an anomalous trough centered near 30°W in November–December, and positive (respectiv…
Sahel droughts and Enso dynamics
1996
Correlations between summer Sahel rainfall and Southern Oscillation Index has increased during the last thirty years. At high frequency time scale (periods lower than 8 years), an intertropical Atlantic zonal divergent circulation anomaly is forced by the difference of sea surface temperature (SST) anomalies between the eastern equatorial parts of Pacific and Atlantic. This zonal connection worked well during most of the E1 Nino/Southern Oscillation (ENSO) events occurring after 1970; positive/negative SST anomalies in the eastern Pacific/Atlantic led to rainfall deficits over the whole West Africa. At low frequency time scale (periods greater than 8 years), positive SST anomalies in the In…
The West African Monsoon Modeling and Evaluation project (WAMME) and its First Model Intercomparison Experiment
2008
International audience; This paper presents the scientific challenge in West African monsoon (WAM) simulation and discusses the West African Monsoon Modeling and Evaluation project (WAMME) initiative and its approaches to improve WAM simulations. Major scientific highlights from the first WAMME model comparison are the focus of the paper. Based on the first WAMME experiment, the WAMME models' performance is evaluated with precipitation being the major focus. The analyses indicate that the models with specified SST generally have reasonable simulations of the mean spatial distribution of WAM precipitation but largely fail to produce proper daily precipitation frequency distributions. WAMME m…
Past and future spatio-temporal variability of rainfall of the Bani catchment in West Africa.
2011
6 pages; International audience; Since 1970, on the Bani, main tributary of the upper Niger, annual discharges have decreased by 69% while annual rainfall has decreased only by 15% to 25% over the catchment. Among the possible causes for this very strong discharge decrease changes of precipitation patterns must be explored. Four different methods of spatial interpolation of rainfall fields were compared on intra-seasonal indices (number of dry days, the dry spells, EDI, SPI, etc.) for the period 1950-2006. This study was also conducted on simulated pluviometric data generated by a regional climatic model (WRF) for the 2032-2041 period. The pluviometric deficit is explained by a conjunction …