Search results for "African Monsoon"
showing 8 items of 8 documents
Calcareous nannofossil palaeoenvironmental reconstruction and preservation in sapropel S1 at the Eratosthenes Seamount (Eastern Mediterranean)
2019
Abstract The most recent organic carbon-enriched layer (sapropel S1) deposited at the Eratosthenes Seamount has unique features, such as an early lithological interruption, fine light silt laminae and an exceptional vertical extent that is over 25 cm thick. Here we investigate calcareous nannofossil assemblages to reconstruct very high-resolution palaeoenvironmental and palaeoceanographic variations recorded before, during and after the perturbation episode that involved the eastern Mediterranean Sea, due to the massive freshwater discharge via Nile River. Our results show that the deep chlorophyll maximum development, observed in all micropalaeontological groups from previous studies, is a…
Monsoon Multidisciplinary Analysis (AMMA) : an integrated project for understanding of the West African climate system and its human dimension
2011
International audience; The intraseasonal time scale is critical in West Africa where resources are highly rainfall dependent. Three main modes of variability have been identified, two with a mean periodicity of 15 days and one with a mean periodicity around 40 days. These modes have a regional scale and can strongly influence precipitation and convective activity. They are mainly controlled by atmospheric dynamics and land-surface interactions. They can also modulate the very specific phase of the African summer monsoon onset. A better knowledge of the mechanisms controlling this scale is necessary to improve its predictability.
Advances in understanding mineral dust and boundary layer processes over the Sahara from Fennec aircraft observations
2015
Abstract. The Fennec climate programme aims to improve understanding of the Saharan climate system through a synergy of observations and modelling. We present a description of the Fennec airborne observations during 2011 and 2012 over the remote Sahara (Mauritania and Mali) and the advances in the understanding of mineral dust and boundary layer processes they have provided. Aircraft instrumentation aboard the UK FAAM BAe146 and French SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) Falcon 20 is described, with specific focus on instrumentation specially developed for and relevant to Saharan meteorology and dust. Flight locations, aims and associated met…
Interannual and decadal SST-forced responses of the West African monsoon
2010
International audience; We review the studies carried out during the African Monsoon Multidisciplinary Analysis (AMMA)-EU on the changes of interannual sea surface temperature (SST)-West African monsoon (WAM) covariability at multidecadal timescales, together with the influence of global warming (GW). The results obtained in the AMMA-EU suggest the importance of the background state, modulated by natural and anthropogenic variability, in the appearance of different interannual modes. The lack of reliability of current coupled models in giving a realistic assessment for WAM in the future is also stated.
The climate change effect on the african monsoon region : evolution of the precipitation and atmospheric fields in the CMIP3 and CMIP5 simulations un…
2013
The fourth IPCC report in 2007 established the synthesis of previously published work onthe effects of climate change on global and regional scales. It shows in particular that no consensuscan be found with regard to the future of rainfall — and atmospheric dynamics- associatedwith region — African monsoon. This dissertation revisits this issue in the light of new dataand using an approach avoiding over-representation of the number of simulations available forone type of model and taking into account the diversity of models and their evolution in time :twenty general circulation models (GCMs) participating in the exercises CMIP3 (twelve GCMs)and CMIP5 (eight GCMs) under the A1B emissions sc…
Changes in the African monsoon region at medium-term time horizon using 12 AR4 coupled models under the A1b emissions scenario.
2011
This study documents simulated precipitation and circulation changes through the 20C3M and A1b scenarios. It portrays a robust pattern, associating rainfall deficits in subtropical regions with rainfall excesses over West Africa, except in Northern Senegal and Mauritania, with a significant enhancement of both the April–June rainy season in 10/12 models and of the July–September rainy season in 8/12 models. Eastward to 5°W a northward shift in the latitude of the moisture flux convergence at 850 hPa is evident in 10/11 models (+0.58° in mean) and a southward shift in 6/11 models in the western region (−0.24°) is observed. Copyright © 2011 Royal Meteorological Society
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 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…