No. 115/2023

Photo: Humboldt Foundation/Frank Siemers Using computer simulations, researchers can both predict the climate in the coming decades as well as produce short-termweather forecasts for specific regions. But so far, they are not as precise as they might be. In order to calculate the complex processes in the atmosphere and identify local extreme weather events such as heavy rain at an early stage, enormous computing capacity is required. New supercomputers could provide it. The atmospheric physicist Bjorn Stevens is working on it. In 2022 at his institute in Hamburg, for instance, “Levante” went into operation.The supercomputer can handle 14 quadrillion operations per second. “It will enable us to do long-term simulations with climate models with a grid resolution of three kilometres, for example,” says Stevens. The researcher is modifying Levante’s code so that simulations run at their optimum. Up to now, global simulations based on models with such fine grids could only be achieved for up to a few months. Levante, however, will make them calculable for several years. But if you want to understand how heavy rainfall will change with global warming, for example, you need computers that are hundreds of times more powerful than Levante. Stevens and some of his colleagues are calling on climate computing centres internationally to join forces inorder to get access to this newgenerationof supercomputers. In 2024, a machine of this kind is scheduled to go into operation at Forschungszentrum Jülich. Text JAN BERNDORFF In 1998, PROFESSOR DR BJORN STEVENS was a Humboldt Research Fellow at the Max Planck Institute for Meteorology in Hamburg where he is now the managing director. HOW PRECISELY CAN SUPERCOMPUTERS FORECAST HEAVY RAINFALL, MR STEVENS? 9 HUMBOLDT KOSMOS 115/2023