Search results for "AFRICA"
showing 10 items of 962 documents
Notes on Afrotropical Cydnidae (Heteroptera) with emphasis on vehicle-mounted net samples and description of a new species from Liberia, West Africa
2019
Notes on the Cydnidae fauna in Liberia, sampled with a vehicle-mounted net, the species taxonomy and general distribution are reported, including the description of Chilocoris elongatus sp. nov. In addition, new country records are provided for Angola, Ethiopia, Gabon, Guine a-Bissau, Namibia, Niger, Republic of South Africa, Sierra Leone, Tanzania, Togo, Uganda, and Zimbabwe.
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 …
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…
Timing and patterns of ENSO impacts in Africa over the last 30 years: insights from Normalized Difference Vegetation Index data.
2012
International audience; In this study we reassess and provide a more complete picture of the timing and patterns of ENSO impacts for the whole of Africa over the three last decades. We analyse the vegetation photosynthetic activity estimated by the NOAA-AVHRR Normalized Difference Vegetation Index (NDVI) rather than rainfall itself, because NDVI allows us to document the impacts at fine space and time scales. The use of the monthly time-step adds important new insights to the findings of previous works based largely on annual or seasonal time-scales and on a regional spatial-scale: several dipolar and propagative patterns are highlighted. In addition, we show that the less-studied winter ra…
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 …
Variations in intensity of the westerly monsoon-like flow from the tropical Atlantic and summer rainfall over equatorial and tropical southern Africa
2009
International audience; An empirical orthogonal function (EOF) of the onshore flow of moisture along the west coast of southern Africa using NCEP-DOE AMIP-2 re-analyses suggests two dominant modes of variability that are linked to: (a) variations within the circulation linked to the mid-latitude westerlies and the South Atlantic anticyclone, (b) the intensity of the westerly flow from the tropical Atlantic. The second mode, referred to as the Equatorial Westerly mode, contributes the most to moisture input from the Atlantic onto the subconti-nent at tropical latitudes. This mode appears to be associated with large-scale rainfall anomalies over the upper lands surrounding the Congo basin in …
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…
Wet periods along the East Africa Coast and the extreme wet spell event of October 1997
2008
Extreme wet spells affect the East Africa Coast (EAC) during March to June (long rains) and October to December (short rains). While these spells are less frequent during the short rains, some of the most extreme wet spells occur at this time of the year. The present study examined the general characteristics of the wet spells during the short rains. A detailed study of the anomalous wet spell event of October 1997, with record rainfall around Mombasa (4.0°S, 39.6°E), was also carried out. Daily rainfall for 1962-1997 and NCEP2 reanalysis data for 1979-1997 were used to study the characteristics of the wet events. A high spatial coherence is found in the rainfall over the EAC. The circulati…
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…