Session
Fahrplan 34C3
Science

On the Prospects and Challenges of Weather and Climate Modeling at Convection-Resolving Resolution

Saal Borg
David Leutwyler
The representation of thunderstorms (deep convection) and rain showers in climate models represents a major challenge, as this process is usually approximated with semi-empirical parameterizations due to the lack of appropriate computational resolution. Climate simulations using kilometer-scale horizontal resolution allow explicitly resolving deep convection and thus allow for an improved representation of the water cycle. We present a set of such simulations covering Europe and global computational domains. Finally, we discuss challenges and prospects climate modelers face on heterogeneous supercomputers architectures.

Today the evidence for global climate change is unequivocal, and the human influence is clear. Therefore the focus of young researchers has shifted from assessing whether the Planet is warming towards envisioning how a warmer world might look like. For instance, basic physical principles suggest that the hydrological cycle of Planet Earth will likely undergo dramatic changes. However, understanding and describing the involved processes, estimating future changes, and assessing the underlying uncertainties has proven to be difficult and complex. In this effort, numerical simulations of the weather and climate system are a useful research tool. Weather and climate modeling involves solving the governing equations of atmospheric motion on a numerical mesh and employing semi-empirical parameterizations that treat the processes not represented explicitly. For example, the parameterizations typically include treatments for thunderstorms and rain showers (deep convection). These processes are fundamental to the climate system since they vertically redistribute moisture, heat, and momentum, but so far they could not be resolved explicitly, due to the coarse gird spacing of the mesh (resolution) employed in the current generation of climate models. In the recent year's power constrains in the domain of supercomputing have lead to heterogeneous node designs mixing conventional multi-core processors and accelerators such as graphics processing units (GPU’s). These machines posses properties beneficial for weather and climate codes and hence allow refining the resolution of the involved computational mesh to the kilometer scale. Convective clouds can then be represented explicitly (convection-resolving) and the models can be formulated much closer to physical first principles. However, to exploit the capabilities of these supercomputers, model codes have to be ported, a challenging task the weather and climate modeling community is struggling with.

We discuss prospects and challenges climate modelers face on these new supercomputers and highlight the potential for addressing key open science questions. The presentation is illustrated with simulations recently accomplished using a new version of the Consortium for Small-Scale Modeling weather and climate model (COSMO), capable of exploiting these heterogeneous supercomputer architectures. Using results form a then-year-long climate simulation on a computational domain covering Europe (1536x1536x60 grid points) we highlight some of the added value of the approach regarding the representation of precipitation processes. Furthermore, we explore the gap between the currently established regional simulations and global simulations by scaling the GPU accelerated version of the COSMO model to a near-global computational domain. References: Fuhrer, O., Chadha, T., Hoefler, T., Kwasniewski, G., Lapillonne, X., Leutwyler, D., Lüthi, D., Osuna, C., Schär, C., Schulthess, T. C., and Vogt, H.: Near-global climate simulation at 1 km resolution: establishing a performance baseline on 4888 GPUs with COSMO 5.0, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-230, in review, 2017. Leutwyler, D., Lüthi, D., Ban, N., Fuhrer, O., and Schär, C.: Evaluation of the Convection-Resolving Climate Modeling Approach on Continental Scales, J. Geophys. Res. Atmos., 122, doi:10.1002/2016JD026013 Leutwyler, D., Fuhrer, O., Lapillonne, X., Lüthi, D., and Schär, C., 2016: Towards European-scale convection-resolving climate simulations with GPUs: a study with COSMO 4.19, Geosci. Model Dev., 9, 3393-3412, doi:10.5194/gmd-9-3393-2016.

Additional information

Type lecture
Language English

More sessions

12/27/17
Science
hanno
Saal Clarke
We're supposed to trust evidence-based information in all areas of life. However disconcerting news from several areas of science must make us ask how much we can trust scientific evidence.
12/27/17
Science
Saal Clarke
Quantitative science evaluation, such as university rankings, rely on man-made algorithms and man-made databases. The modelling decisions underlying this data-driven algorithmic science evaluation are, among other things, the outcome of a specific power structure in the science system. Power relations are especially visible, when negotiated during processes of boundary work. Therefore, we use the discourse on 'citation cartels', to shed light on a specific perception of fairness in the ...
12/27/17
Science
manuel
Saal Clarke
For a few decades by now, satellites offer us the tools to observe the whole Earth with a wide variety of sensors. The vast amount of data these Earth observations systems collect enters the public discourse reduced to a few numbers, numbers like 3 or even 300. So, how do we know the amount of ice melting in the arctic or how much rain is falling in the Amazon? Are groundwater aquifers stable or are they are being depleted? Are these regular seasonal changes or is there a trend? How can we even ...
12/27/17
Science
Steini
Saal Clarke
Jeder kennt sie, kaum jemand versteht sie wirklich, die vielleicht berühmteste Gleichung der Welt: E=mc^2 Was hat es damit auf sich, was ist die spezielle- und was die allgemeine Relativitätstheorie? Wie kann man sicher sein, dass das wirklich stimmt? Bleibt die Zeit stehen, wenn man sich mit Lichtgeschwindigkeit bewegt? Was ist das Zwillings-Paradoxon und dehnt sich das Universum aus, oder werden wir einfach nur immer kleiner?
12/28/17
Science
Saal Adams
Eine wissenschaftliche Perspektive auf die achtlose Anwendung der Algorithmen des maschinellen Lernens und der künstlichen Intelligenz, z.B. in personalisierten Nachrichtenempfehlungssystemen oder Risikosoftware im US-Justizsystem.
12/28/17
Science
Thorsten
Saal Dijkstra
Wouldn’t it be awesome to have a microscope which allows scientists to map atomic details of viruses, film chemical reactions, or study the processes in the interior of planets? Well, we’ve just built one in Hamburg. It’s not table-top, though: 1 billion Euro and a 3km long tunnel is needed for such a ‘free electron laser’, also called 4th generation synchrotron light source. I will talk about the basic physics and astonishing facts and figures of the operation and application of these ...
12/29/17
Science
Friedemann Reinhard
Saal Dijkstra
Holography of Wi-Fi radiation Philipp Holl [1,2] and Friedemann Reinhard [2] [1] Max Planck Institute for Physics [2] Walter Schottky Institut and Physik-Department, Technical University of Munich When we think of wireless signals such as Wi-Fi or Bluetooth, we usually think of bits and bytes, packets of data and runtimes. Interestingly, there is a second way to look at them. From a physicist's perspective, wireless radiation is just light, more precisely: coherent electromagnetic radiation. It ...