SMART-TWIN: Setup and Application of the Urban Climate Model PALM-4U for the City of Würzburg

This work presents the EU-funded project “SMART-TWIN - AI-supported planning tool for a climate-adapted green urban development in Bavaria”. Climate resilience in urban planning is becoming increasingly important, especially regarding the adaption to extreme weather events and mitigation of associated risks. For a more sustainable and efficient urban and land-use planning, the SMART-TWIN project develops an AI-supported digital planning tool for the city of Würzburg. Main objective of the project is the extension of the existing digital twin by integrating the urban climate model PALM-4U. This tool enables local authorities and planning offices to simulate different scenarios for real or potential construction projects as well as modifications to green and blue infrastructure, and to assess their impacts on the urban climate, under both current and prospective (extreme) weather conditions. This way, planning processes can be carried out with greater precision, speed, and cost-efficiency. Würzburg offers particularly suitable conditions for this project: its warm and dry climate, dense building structures, and low proportion of green spaces make the city a climate change hotspot in Central Europe. 

As a practical contribution to the planning tool, we provide our own simulations for typical climate and urban planning scenarios for five public areas in Würzburg at a spatial resolution of 1 m:  For this purpose, we implement modifications of the urban infrastructure by creating real or potential building projects, such as the unsealing of parking areas, tree plantings on town squares or along major roads, changes in surface albedo, or the conversion of sealed areas into inner-city parks. In addition, a selection of characteristic (extreme) weather conditions is considered for each planning scenario, including a heat day, a tropical night or a day with intense solar radiation. The climate impact on the entire city area is represented at a spatial resolution of 10 m.  

The simulations are driven by boundary conditions from the COSMO-CLM 5.10 Model with hourly resolution for the period January to December 2019. The preliminary PALM-4U configuration and domain setup promise comprehensive results for the early identification of urban hotspots and urban heat island patterns and the positive effect of shading and urban vegetation.