ZIH-Colloquium 2026

The ZIH colloquium is a public event and takes place usually the 4th Thursday of each month. Below you will find the current and former dates with all necessary information. You are cordially invited!

23 April 2026, 3:00 p.m., APB-1096/ Online BBB
Prof. Dr. Siegfried Raasch (Department of Meteorology and Climatology, IMUK, Leibniz University Hannover, Germany; Pecanode GmbH) - "The PALM Model System Release 25.10 - An LES Code for Basic and Environmental Research – Capabilities and Recent Applications"

Originally applied to study the convective atmospheric boundary layer (CBL), largeeddy
simulation (LES) is now used in many areas of science. This is mainly due to a
substantial increase in available computing resources. State-of-the-art massively
parallel computers have opened the field to a wide variety of new applications. On
these machines, simulations with extremely large numerical grids - up to 40003 grid
points and beyond - are currently performed within acceptable timeframes. In
Meteorology, besides for the fundamental research on neutral and stable stratified
flows, where the typical eddy size is much smaller than in purely convectively driven
flows, LES is increasingly used for more applied topics such as air-pollution
modeling, flow around buildings, wind energy, and aircraft operation.

The LES model PALM (PArallelized LES Model), originally developed at the Leibniz
University Hannover (LUH), has become a community model over the last 10-15
years. Besides LUH, a team of national and international developers has significally
extended the original code with a wide range of features, including cloud physics,
chemistry, radiation, Lagrangian particles, and various nesting capabilities. A strong
focus is placed on the explicit representation of detailed surface processes, e.g.
resolved-scale vegetation and the complex geometry of buildings. PALM is well
optimized for state-of-the-art cache-based and vector processors and scales
efficiently up to 40.000 cores and beyond. The code is currently ported to run on
GPUs.

The talk will start with a short general introduction to atmospheric turbulence and
LES, and then provide an overview of PALM’s features, illustrated by results from
recent studies at IMUK.

Siegfried Raasch was a professor of theoretical meteorology at Leibniz University
Hannover until his retirement in 2024. He is now an employed by Pecanode GmbH,
where he continues to develop and maintain the PALM model, which he initially
began developing in 1997. His research interests focus on atmospheric boundary
layer turbulence, large-eddy simulation, and the optimization of numerical algorithms.

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