A Model-based Investigation of Climate Variability and Climate Change: Focus on the West African Monsoon System

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The project will assess climate variability and climate change of the West Africa (WA) summer monsoon, based on the analysis of simulations of Regional Model version #3 (RM3) of the Columbia University Center for Climate Systems Research. The investigators will (i) determine the optimum configuration of the RM3 for simulating projections of WA climate change, (ii) investigate the interannual variability of WA monsoon onset and African easterly wave activity and how they relate to droughts, and (iii) compute trends in WA precipitation, temperature and monsoon onset date. Model climate change projections during the 21st century will be forced by several global climate models, for each of two greenhouse gas emissions scenarios. RM3 climate projections will be analyzed on a 0.44° (~50 km) grid over Africa for two 30-year periods, 2011-2040 and 2041-2070 by comparing these results to a parallel simulation for a base period, 1981-2010. Results will be shared in a new international collaboration, a COordinated Regional climate Downscaling Experiment (CORDEX), an initiative of the World Climate Research Project (WCRP) of the United Nations. This work will provide more credible projections of WA climate trends, given large uncertainties in projecting how water availability in WA will evolve throughout the 21st century by current climate models. It will provide the first continuous multi-year climatologies of RM3 regional model simulations, for the contemporary and future climate. The proposed research on monsoon onset and on the analysis of African easterly waves will advance the development of seasonal forecasting techniques. The participation in WCRP CORDEX will advance the science of analyzing climate change on a regional scale. From the perspective of broader impacts, this project will contribute to the CORDEX objective of greater interaction and communication between global climate modelers, the downscaling community and end-users, to better support impact/adaptation activities benefiting Africa's vulnerable population. RM3 simulation results archived by CORDEX will provide data for model intercomparison studies. Model development achievements will be shared with the African Center of Meteorological Applications for Development (ACMAD) in Niamey, Niger, and applied to promote ACMAD RM3 weather and climate guidance simulations, which are made available to users throughout Africa.