From weather forecasting to climate simulation

Von der Wettervorhersagezur Klimasimulation — So genau wie die Wettervorhersage für morgen: Wohin entwickelt sich das weltweite Klima in 20, 30 Jahren?

A typical application that would have been inconceivable for decades without the computing power of supercomputers is weather forecasting. Germany’s National Meteorological Service (DWD) uses the ICON atmospheric model, a modular open-source software.

The software can be used to calculate short periods of time with a high spatial resolution, enabling weather forecasts to be made for the coming days based on current measurements and observations. It is also possible to work with a lower resolution and simulate the development of the global climate over decades. “However, we want to look much further and more accurately into the future – creating detailed, long-term climate forecasts,” explains meteorologist Dr. Sabine Griessbach (JSC).

How will the global average temperature change if we continue to pump CO₂ into the atmosphere? And what about extreme weather events? Will we experience heat waves more frequently in future? And with what intensity?

Thanks to JUPITER’s computing power, ICON will be able to answer these questions with greater accuracy than ever before. The crucial advantage that JUPITER offers the model is a smaller mesh size. ICON covers the Earth in a grid of triangles. It then calculates the relevant parameters such as temperature, pressure, and humidity for each of these grid cells. The mesh size of the network indicates approximately how wide an individual triangle is. For current weather forecasts with ICON, the mesh size is around 13 kilometres. This means that phenomena with a smaller scale, such as clouds, can fall through the cracks, so to speak.

“With JUPITER, we can change that and simulate the future of the climate with a spatial resolution of about one kilometre,” explains Dr. Lars Hoffmann (JSC), an expert in atmospheric research and modelling: “We can thus bridge the gap between weather and climate modelling. And extreme events such as violent thunderstorms and heavy rainfall will be depicted much more realistically on the computer than they are today.” Initial work on this has already started on the JEDI test system.

An important aspect will be how the weather and climate models work with the latest generation of graphics cards used in JUPITER. “For example, many software libraries also need to be installed. We are currently in the process of configuring, testing, and optimizing them so that we can use the computer architecture as efficiently as possible,” explains Grießbach.

JEDI is the first module of JUPITER. It already features the hardware that is planned for the JUPITER Booster module. As with the JUPITER Booster module, JEDI uses particularly efficient GPUs from the world’s leading chip manufacturer, NVIDIA.