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.

Regional climate simulations at the convection-permitting scale (< 4 km) have the potential to improve seasonal forecasts, especially where complex topography hinders global models. Due to high computational costs, tests using state-of-the-art ensemble forecasts have not been performed yet. In this one-year case study, a Weather Research and Forecasting (WRF) multi-physics ensemble was used to downscale the SEAS5 ensemble forecast over the Horn of Africa. Reliability of precipitation prediction is improved, although the global model’s biases in temperature and precipitation are not reduced. Measurable added value against the global model is provided for intense precipitation statistics over the Ethiopian highlands.

Results from high-resolution simulations with the sea ice-ocean model FESOM, formulated on unstructured meshes, are presented in which ocean eddies are resolved in the North Atlantic region. By resolving ocean eddies, these features are represented by the laws of physics rather than empirical rules of thumb, as done in most existing climate simulations. A comparison with satellite data suggests that the simulated eddy fields start to become indistinguishable from observations, showing that the model passes the climatic Turing Test. It is argued that these high-resolution models have the potential to significantly increase our understanding of how the climate in general and the ocean in particular will be evolve in a warming world.

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.

The SMOC (SubMesoscale Ocean Modelling for Climate) project aimed to shed light on the role of submesoscale turbulent processes in the overall functioning of the ocean. Leveraging HPC power, the researchers in particular tried to get answers to: A) how deep do submesoscale fronts penetrate and can they be a significant source of dissipation for the ocean circulation away from the surface?, and B) to which extent do submesoscale fronts participate in the transfer into the deep ocean of the near-inertial energy injected by the wind at the ocean surface?

Two-phase flows with water droplets greatly affect the thermal-hydraulic behaviour in the containment of a Pressurized Water Reactor (PWR). In order to predict the local thermal-hydraulic behaviour in a real containment in the case of a severe accident, scientists of the University of Stuttgart generated a three-dimensional geometry of a model containment based on a German PWR. 

In order to develop economic, efficient, and reliable wind turbines, the knowledge of the mechanisms that evoke transient aerodynamic loads effecting blades, tower, and the nacelle is essential. Using high performance computing technologies, researchers of the University of Stuttgart used high-fidelity Computational Fluid Dynamics (CFD) methods to accurately predict these unsteady loads. Particular interest was paid on the interaction of wind turbine and atmospheric boundary layer.

Leveraging the high-performance computing capabilities of the HLRS supercomputing infrastructure, scientists of the Theoretical Materials Physics Group of the Paderborn University managed to trace interface defects in amorphous/crystalline silicon heterojunction solar cells. Visualizing the processes with atomic resolution they were able to characterize the processes that compromise the solar cells' efficiency. The findings will help to optimize the solar cells further and to decrease production costs.

Thanks to the availability of HLRS’s petascale HPC system Hornet, researchers of the Institute of Physics and Meteorology of the University of Hohenheim were able to run a highly complex climate simulation for a time period long enough to cover various extreme weather events on the Northern hemisphere at a previously unmatched spatial resolution. Deploying the highly scalable Weather Research and Forecasting (WRF) model on 84,000 compute cores of Hornet, the achieved results confirm an extraordinary quality with respect to the simulation of fine scale meteorological processes and extreme events.

Scientists from the University of Hohenheim (Stuttgart/Germany) aim to investigate and to improve the performance of regional climate simulations in Europe with the Weather Research and Forecast (WRF) model. The model is operated from 12 km down to the convection permitting scale of 3 km, for advancing process understanding.

The flow in the earth's atmosphere involves many complex features. One of these features are so-called gravity waves. They become important as soon as they break somewhere in the atmosphere, since this breaking results in a strong patch of turbulence for no apparent reason. In order to improve the basic understanding of the breaking process, scientists conducted high-resolution simulations of different types of gravity-wave breaking events.

Using the computing capabilities of HLRS system Hermit, a team of scientists used the Community Earth System Model (CESM) with a strongly eddying ocean submodel to study the presence of ocean eddies on the sensitivity of the Meridional Overturning Circulation (MOC) in the Atlantic Ocean to the Greenland Ice Sheet (GrIS) freshwater anomalies.

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.

Scientists use GCS supercomputers for compute-intensive simulations in order to increase the fidelity of global climate simulations and provide quantitative information about the frequency of high-impact events and their risks. The research activity comprises a large series of global experiments (an ensemble), with each member of the ensemble dynamically simulating 27 years of both current and future climates.

Concerns about the present global energy situation and the impacts of climate change are the driving forces for optimizing combustion power plants operation towards maximum efficiency, and thus minimizing the emission of greenhouse gases. Computational modelling of the combustion process in industrial scale combustion systems has become a key technology to achieve this ambitious goal.