Extreme weather events, like heavy precipitation, heat waves, droughts and wind storms have a detrimental impact on East African societies. The Lake Victoria Basin (LVB) is especially vulnerable: It is estimated that each year 3,000-5,000 fishermen perish on the lake due to nightly storms (Red Cross, 2014). In addition, the LVB is a global hotspot of future population growth and urbanization. Urban dwellers in this region with low infrastructure are particularly vulnerable to climate extremes, such as urban flooding. As the frequency and intensity of climate extremes is projected to further increase substantially with climate change, so do the risks, with potentially major consequences for livelihoods of people in the LVB.
Future climate projections for the LVB are challenged by the complexity of the region. The mesoscale circulation induced by the lake and by the complex orography surrounding the basin, strongly modulate the climate change signal. Moreover, current state-of-the-art climate simulations over the region parameterise convection, while Convection Permitting Models (CPMs) have shown a strong added value in representing convection in other regions of the world. Altogether this urges for reducing model resolution to grid sizes of less than 5 km. The computational cost of CPM integrations is currently so high that individual groups can only afford one realization of a possible future climate. Ensemble climate projections at the CPM scale are only possible in internationally coordinated programmes such as CORDEX. We therefore propose the CORDEX Flagship Pilot Study (FPS) “ELVIC - climate Extremes in the Lake VICtoria basin” with the overall objective to provide robust climate information on extremes to the impact community. Thereby, ELVIC answers the following questions:
· Are moist convective systems in Equatorial Africa better represented by CPMs compared to models that rely on a parametrization of convection?
· How can we best combine information of CMIP and CORDEX-Africa with CPM (climate change) integrations?
· How will extreme weather events evolve in the future in the LVB?
· How can improved probabilistic information on convective extremes be used by the impact community?
An assessment of the capability of CPMs to represent extremes is only possible when sufficient observational data are available. With the recently endorsed Hydroclimate project for Lake Victoria (HyVic) and the UK-led project HyCRISTAL (Integrating Hydro-Climate Science into Policy Decisions for Climate-Resilient Infrastructure and Livelihoods in East Africa), observations are planned in the region. This, together with the emergence of a group of scientists planning or already performing CPM integrations in the region makes ELVIC
extremely timely. This FPS is an effort to coordinate activities between these groups.
With this FPS we want to improve climate change adaptation strategies in the LVB by providing useful climate information for stakeholders and impact assessment teams.