Statistical Downscaling for Precipitation Projections in West Africa

Abstract The West Africa region (5to 20N and 10E to 20W) is particularly vulnerable to climate change due to a combination of unique geographic features, meteorological conditions, and socio-economic factors. Drastic changes in precipitation (e.g., droughts or floods) in the region can have dramatic impacts on rain-fed agriculture, water availability, and disease risks for the region's population. Quantifying these risks requires localized climate projections at a higher resolution than is generally available from global climate models. Using Self-Organizing Maps, we produce station-based downscaled precipitation projections for medium and high-emission climate scenarios for this region. We find slight increases in precipitation in the coastal areas, and decreases in the interior Sahel region by an average of 10\% by 2100 under the high greenhouse gas-emission scenario of Shared Socioeonomic Pathway 5-8.5. Precipitation decreases in the Sahel are primarily driven by reductions in the number of rainy days during the wet season, rather than by consistent decreases in the magnitude of the precipitation amounts or decreases in the average length of the wet season.