ENVIRONMENT AND ENERGY

The African Continent will be severely hit by climate change. A necessary building brick for counteraction are reliable projections of the African climate of our century. The CORDEX CORE initiative is designed to provide such information for the CORDEX CORE regions, among them CORDEX CORE Africa. IMK-TRO contributed to this with an ensemble of presently ten regional climate simulations performed on the Hazel Hen at HLRS Stuttgart. Results indicate dramatic changes especially in precipitation. The simulations presented here will be part of the IPCC AR6 atlas of regional climate change and the CORDEX data repository. They will be freely available for impact, adaptation and mitigation studies.

To avoid dangerous climate change, we have to reduce the emission of greenhouse gases radically. This requires – among other measures – an increase of renewable sources of energy like solar and wind. In 2019, already a quarter of Germanys electricity demand has been met by wind power. In order to increase this share, one has to develop sites in hilly terrain. High resolution models are required to assess the suitability of candidate sites with respect to turbulence intensity, power production and variability. This project supports the development of the test-site WINSENT, which is located on the Swabian Alp near Stuttgart.

Using the Model for Prediction Across Scales (MPAS), four years of climate simulations at convection-permitting resolutions where carried out using a variable 30-3km resolution mesh, transitioning the so-called gray zone of convection around 5-10km. The comprehensive data set generated following the protocol of the CORDEX Flagship Pilot Study (FPS) on convection-permitting climate simulations will allow the CORDEX-FPS community to study the added value of global, variable-resolution simulations down to convective scales over traditional approaches employing regional climate models and/or coarse horizontal resolutions.

Modelling of the regional present day as well as future climate is of great interest both scientifically as well as for applications. The “Regional Climate and Water Cycle Group” at KIT Karlsruhe uses the COSMO-CLM regional climate model for detailed climate simulations in various parts of the world. Many of these quite expensive and storage intensive runs are performed on Hazel Hen at HLRS. After giving a motivation for high resolution climate modelling, the scientists briefly describe some technical aspects like nesting and ensemble building and then go to a short presentation of some results concerning the future climate in Baden-Württemberg.

Gas exchange across water surfaces receives increasing attention because of its importance to the global greenhouse budget. At present, most models used to estimate the gas flux only consider wind-shear. To improve the accuracy of the predictions a detailed study of buoyancy-driven gas transfer, which is a major contributor at low to moderate wind-speed, is necessary.  The main challenge lies in resolving the extremely thin gas concentration boundary layer. To address this, direct numerical simulations (DNS) of gas transfer induced by surface-cooling were performed on SuperMUC using a numerical scheme that is capable of resolving the thin diffusive layers on a relatively coarse mesh while avoiding spurious oscillations of the scalar…

Scientists of the Institute for Hydrodynamics of the Karlsruhe Institute of Technology (KIT) have – for the first time – performed high-fidelity numerical simulations of the formation of sediment patterns in a channel flow configuration.

Atmospheric processes and climate change take place on all spatial scales: global, continental down to regional or local scales. Not only do processes on the different scales differ from each other but also regions exhibit various characteristics. Regional and local climate as such depends on small-scale structures such as urbanisation, land use, soil types, water surfaces, orography and vegetation.

The gas transfer process across the air-water interface plays an important role in many industrial and environmental systems. Very thin diffusive layers mark the interfacial mass transfer of low-diffusive substances. Using simulation technologies, scientists try to achieve a good understanding of the physical processes by resolving the gas transfer in these thin layers.