Case study simulation of the green infrastructure influence on heat stress with urban climate model PALM-4U

City planners have to take multiple considerations and prospective issues into account when an urban area is to be developed. Especially in the cities, the heat island effect and the high population density combine to a health threat during heatwaves. Climate change exacerbates this heat stress and continues to do so for decades – a time scale relevant in urban planning. The increasing necessity to include urban climate adaption measures requires valid arguments for the decision-making process where they are in competition with other use of scarce urban space.

Urban climate models are a tool for assessments of the heat stress, wind comfort, the dispersion of pollutants and others – be it already built or only a proposed plan. The high-performance LES model PALM allows for modelling the atmospheric boundary layer from a whole-city level to a block of houses in resolutions up to 2 m. The model system PALM-4U can be adapted to the assessment question of interest by activating modules like urban surfaces. This incorporates, for example, urban green infrastructure from trees to façade greenery in the simulation. 

In this presentation, we show an application case for the model PALM-4U to assess a common planning question taken from municipal practice. The simulations investigate the impact of a high degree of green and blue infrastructure compared to a low degree in the plans of a development area. Climate adaption measures like façade greening, replacement of pavement with grass and ponds are evaluated in their cumulative effect on thermal comfort indices PT, PET and UTCI.

These simulations are part of the research project “ProPolis” that seeks to bridge the gap between science and practice in urban climate modelling by operationalizing PALM-4U into a practicable and user-friendly tool tailored towards the needs of municipalities and urban planners. ProPolis is part of the research and development program “Urban Climate Under Change [UC]²” funded by Germany’s Federal Ministry of Education and Research (BMBF).