Errors and uncertainties introduced by a regional climate model in climate impact assessments: example of crop yield simulations in West Africa

16 pages; International audience; The challenge of estimating the potential impacts of climate change has led to an increasing use of dynamical downscaling to produce fine spatial-scale climate projections for impact assessments. In this work, we analyze if and to what extent the bias in the simulated crop yield can be reduced by using the Weather Research and Forecasting (WRF) regional climate model to downscale ERA-Interim (European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis) rainfall and radiation data. Then, we evaluate the uncertainties resulting from both the choice of the physical parameterizations of the WRF model and its internal variability. Impact assessments w…

The onset of the rainy season and farmers’ sowing strategy for pearl millet cultivation in Southwest Niger

A multi-year (2004-2009) field survey of on-farm sowing practices in 10 villages located in south-west Niger close to Niamey, is analysed to investigate the relationships (i) between rainfall and the sowing date of pearl millet and the risk of sowing failure, (ii) between sowing and meteorological/agro-climatic onset dates, (iii) between sowing/onset dates, and simulated and observed yield/biomass at the end of the season. Even if some villages sow without any synchronous or anterior rainfall, most parcels (73% out of the 1551 available cases) are sown during and just after a 2-day wet spell receiving at least 10 mm. In fact, there is a strong correlation (r = 0.82-0.95 depending on onset d…

Downscaling West African climate : uncertainties, sensitivity to the model physics and regional variability

We present here a set of regional climate simulations, complementary to the CORDEX-Africa modeling exercice, performed over West Africa during the 1989-2010 period using the non-hydrostatic model WRF. Lateral and SST forcings are provided by ERA-Interim reanalyses. The regional domain [45W 45E 10S 30N] encompasses West Africa and the nearby Atlantic Ocean and Gulf of Guinea. The grid resolution is moderate (80km, with 28 levels on the vertical) in order to reduce computational costs and multiply sensitivity experiments. A first set of fifteen 20-year long simulations addresses the influence of the model physics (convective, radiative and land surface schemes). A second set of simulations co…

Monsoon Multidisciplinary Analysis (AMMA) : an integrated project for understanding of the West African climate system and its human dimension

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.

Analysis of the relationships between climate/aerosols and meningitis epidemics in Western Africa

Advances in the analyses of dust/climate and meningitis relationships based on a multidisciplinary approach

International audience

Vulnerability and adaptation of agriculture to climate variability and change in the Sahel: results from the AMMA program

Ethnographic context and spatial coherence of climate indicators for farming communities : a multi-regional comparative assessment

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 the main resultsof a multi-disciplinary ethnographic and climatic project (PICREVAT). Its main objective was to seek the climatic information ? beyond the seasonal amounts ? critical for crops, both as an actual constraint to crop yields and as identified by the current and past practices and perceptions of farmers. A second goal was to confront t…