Search results for "Clima"
showing 10 items of 6069 documents
Seasonal reproducibility and predictability of the West African Monsoon in coupled GCMs
2009
In the framework of the ENSEMBLES FP6 project, an ensemble prediction system based on five different state-of-the-art European coupled models has been developed. This study evaluates the performance of these models for forecasting the West African monsoon (WAM) at the monthly time scale. From simulations started the 1 May of each year and covering the period 1991–2001, the reproducibility and potential predictability (PP) of key parameters of the WAM—rainfall, zonal and meridional wind at four levels from the surface to 200 hPa, and specific humidity, from July to September—are assessed. The Sahelian rainfall mode of variability is not accurately reproduced contrary to the Guinean rainfall …
Multi-scale study of the rainy season onset over the Sudano-Sahelian belt: Spatial coherence and potential predictability
2011
The spatial coherence of boreal monsoon onset (July-September) over the western and central Sahel is studied through the analysis of daily rainfall records for 136 rain-gauges from 1950-2000. Onset of the rainy season has been defined using 3 definitions which rely on 3 overlapped spatial scales: (i) the regional scale, i.e. the northward ITCZ jump from Guinean to Soudano-Sahelian latitudes, (ii) the meso-scale related with the first occurrence of the main rainfall-generating phenomenon, that is squall line and (iii) the local-scale of the first rainfall recorded at the rain-gauge. Local and meso-scale onsets show a weak degree of instantaneous and inter-annual spatial coherence, meaning th…
North-Atlantic Oscillation and regional-scale sea-surge variability in Gulf of Lions during the 20th century
2010
Article soumis; International audience; Sea-surge variations recorded at three tide-gauge stations (Grau-de-la-Dent, Sète, and Port-Vendres) around the Gulf of Lions (Northwest Mediterranean Sea) are mostly locally forced by onshore winds blowing from 90° to 180° related to an atmospheric depression usually centered between the Bay of Biscay and the British Island, which is more prevalent during the negative phase of the North-Atlantic Oscillation (NAO). During the second half of the 20th century, the long-term increase of sea-surge height at Grau-de-la-Dent finds no counterpart in the positive deviation of the NAO. The relationship between the monthly frequency of sea surges > 20 cm at Gra…
Désagrégation dynamique haute résolution spatiale du climat du Centre Est de la France par le modèle climatique régional ARW/WRF
2010
Ce travail analyse les capacités du modèle climatique régional ARW/WRF à reproduire les principaux traits du climat (températures de surface et précipitations) du Centre Est de la France à des résolutions spatiales fines, et pour les années 1991 et 2003. La simulation utilise pour la désagrégation du signal une descente d'échelle basée sur trois domaines emboîtés de maille variable de 120 km, 30 km et 7,5 km. Les conditions latérales sont imposées toutes les 6 heures par les ré- analyses ERA-Interim. Les températures et les précipitations observées par le réseau de mesures de Météo-France Bourgogne sont utilisées pour l'évaluation. Les simulations reproduisent bien la température (R²~0,95 e…
Instability of space-time rainfall regimes in the payment of basin Mono-Couffo and its impact on the flow of 1961 to 2000
2009
International audience; The catchment area of Mono-Couffo complex, is located in the Gulf of Benin, in the southern part of the Republics of Benin and Togo, at the continent-ocean interface. It lies about 526 km from north to south between 06 ° 16 'and 09 ° 20'N and covers an area of 27 870 km ². The analysis of the variation in rainfall totals for the period 1961-2000 in the basin of Mono-Couffo, between Benin and Togo has been a slight decrease in precipitation. This study aims to identify possible changes in the precipitation regime of the basin and their potential impact in the hydrological functioning of river Couffo. The data used are the monthly precipitation of a network of 25 stati…
The role of the eastern Mediterranean sea on the WAM in 2003 using the WRF regional model
2009
International audience; There is empirical evidence that sea surface temperatures (SST) exert a prominent role on the WAM, particularly over the Atlantic ocean where they can act to modify the location of the ITCZ and moisture advection. However, the role of the Mediterranean sea has been studied more recently. Rowell (2003) has first shown that the basin could play a significant role on the monsoon in modifying the moisture transport and convergence of humidity. Using GCM simulations, he demonstrated that warmer (colder) than normal SST on the Mediterranean sea is associated with a more/less intense monsoon in the Sahel region. A simple composite analysis between the SST and the Sahel July…
Weather Regimes in the Euro-Atlantic and Mediterranean sector and relationship with West African rainfall over the period 1989-2008 from a Self-Organ…
2011
International audience; Weather Regimes (WR) have been defined over the Euro-Mediterranean region [60°W-60°E; 15°N-70°N] from May to October season using the daily Sea Level Pressure, 700 hPa geopotential height and specific humidity from ERA-interim over 1989-2008 period. Computations are based on a neural network lassification technique referred to as Self Organizing Maps and the WR produced can be used by the community for comparison with other periods, projection onto model outputs, seasonal prediction or teleconnection studies. The article particularly examines the relationship between WR and West African (WA) rainfall and our results suggest that changes in particular WR frequencies c…