MOSAIK: Mission

The central goal of MOSAIK is the development of a new, modern, user-friendly, highly-efficient, and high resolution urban climate model (UCM), which allows simulations of large cities of size of up to 2.000 km² with grid-resolved buildings. Besides large massively-parallel computers, the model shall also run on local PCs and workstations with limited resources. To achieve this goal, the new model will be based on the modern highly-parallelized large-eddy simulation (LES) code PALM, instead of using one of the existing UCMs that have been used for more than two decades, which are well-established but difficult to adapt to state-of-the-art parallel and future many-core computer architectures. The new UCM will be called PALM-4U.

Model development work flow within MOSAIK

The new model will be able to perform runs for climate scenarios for entire city environments at moderate resolution (about 100 m grid spacing) as well as short episodes such as daily cycles with building-resolving resolution (1-10 m) on large massively parallel computers. Moreover, it will be possible to run the model on desktop PC systems for different applications, e.g., to run planning scenarios for single city quarters.

The aim of the MOSAIK consortium is to deliver PALM-4U, a UCM running one order of magnitude faster (with respect to wall-clock time) on state-of-the-art PCs compared to already existing UCMs.

The new model will follow a strict sustainability concept and will have the following features:

• Magnifying lens function (zoom function) that allows planners to perform high-resolution studies for areas of interest of limited size (city quarters, single building environments).
• Nesting to large scale models.
• Graphical user interface for end users such as city planners, which allows to set up the model, implement planning scenarios, conduct simulations, and visualize the model output data.
• NetCDF as Standard I/O data format.
• Scale-dependent turbulence and building parameterizations to run with varying resolution from 1-100 m.
• LES mode, which allows to estimate turbulence induced fluctuations (e.g. peak concentrations or wind gusts) for the first time with a UCM
• Output of human-related quantities as physiological equivalent temperature (PET) or universal thermal climate index (UTCI) but also use a multi-agent model (MAM) to determine critical hotspots based on the behavior of people.
• A standard catalog of input data for typical weather/climate scenarios, including high-risk scenarios such as heat waves.
• Distribution by Leibniz Universität Hannover as Open Source software.

The new high performance model PALM-4U will not only allow to study climate change impacts on urban areas, it will also enable to develop new city planning strategies to reduce such impacts on humans (e.g. green corridors or roof greening). Due to its Open Source character, the model can also contribute to the improvement of other urban micro- and mesoscale models. A special emphasis will be put on usability and sustainability for daily use by developing an intuitive and easy-to-use graphical user interface. With the MAM approach, an innovative technique will be implemented that allows for incorporating social-economic data into the UCM.