Regional climate model study on the impact of tectonic and orbital forcing on East African climate

Introduction The DFG-funded research group RiftLink (www.riftlink.de) aims at clarifying the causes of rift-flank uplift in the East African Rift System (EARS) since the late Miocene, its impact on climate and the possible consequences for the evolution of hominids. The climate modelling part within RiftLink concentrates on climatic changes caused by different forcing factors. To analyse the impact of these factors, both global and regional climate models are applied. The global coupled atmosphere ocean general circulation model ECHO-G (ECHAM4 and HOPE-G) is used with a horizontal resolution of approx. 3.75°. Its simulations show the impact on larger scales and are used to drive the regional model CLM with a horizontal resolution of approx. 50 km. With this high resolution smallscale changes in forcing factors can be realised and their impact on regional to local climate can be analysed. Two forcing factors influencing East African climate are tectonic forcing represented by changes in the topography of East Africa and orbital forcing represented by changes in the Earth’s orbital parameters. The impact of these forcing factors are analysed with ECHO-G (not shown) and CLM. Regional climate model CLM The non-hydrostatic regional model CLM is the climate version of the regional weather prediction model of the German Meteorological Service and is developed as a community effort of several universities and research centers (www.clm-community.eu). In this study it is applied with a horizontal resolution of 0.5° and 32 vertical layers. The simulation area covers nearly the whole of Southern and Eastern Africa.