The WASCAL regional climate simulations for West Africa – how to add value to existing climate projections

Abstract:

With climate change being one of the most severe challenges to rural Africa in the 21st century, West Africa is facing an urgent need to develop effective adaptation and mitigation measures to protect its constantly growing population. WASCAL (West African Science Service Center on Climate Change and Adapted Land Use) is a large-scale research-focused program designed to enhance the resilience of human and environmental systems to climate change and increased variability. An integral part of its climate services is the provisioning of a new set of high resolution, ensemble-based regional climate change scenarios for the region of West Africa.

In this contribution, we present the overall concept of the WASCAL regional climate projections and provide information on the dissemination of the data. We discuss the model performance over the validation period for two of the three regional climate models employed, the Weather Research & Forecasting Tool (WRF) and the Consortium for Small-scale Modeling Model COSMO in Climate Mode (COSMO-CLM), and give details about a novel precipitation database used to verify the models. Particular attention is paid to the representation of the dynamics of the West African Summer Monsoon and to the added value of our high resolution models over existing data sets. We further present results on the climate change signal obtained from the WRF model runs for the periods 2020-2050 and 2070-2100 and compare them to current state-of-the-art projections from the CORDEX project.

As an example, the figure shows the different climate change signals obtained for the total annual rainfall with respect to the 1980-2010 mean (WRF-E: WASCAL 12km high-resolution run MPI-ESM + WRFV3.5.1, CORDEX-E: 50km medium-resolution run MPI-ESM + RCA4, CORDEX-G: 50km medium-resolution run GFDL-ESM + RCA4).