Assessing the effect of tree cover on Outdoor Thermal Comfort: A Comparative Study for two Local Climate Zones common in Europe

As cities grow, rising temperatures and reduced green spaces contribute to more urban heat stress. Numerous studies confirm that urban tree cover increases Outdoor Thermal Comfort (OTC). However, there are fewer studies available, which confirm the optimal percentage of tree cover in the cities for built-up local climate zones. This study aims to observe and understand how different levels of tree cover (0%, 10%, 20%, 30%, existing tree cover) influence Outdoor Thermal Comfort (OTC) in two local climate zones common in Europe. Kassel, Germany, was selected as a representative mid-sized European city, with LCZ 5 (open mid-rise) and LCZ 6 (open low-rise) as its most frequent built-up local climate zones. We used the ENVI-met microclimate model to simulate temperature conditions for UTCI under the four different tree-cover scenarios to identify optimal tree-cover percentages for reducing heat stress. Since each Local Climate Zone (LCZ) has different layouts, including green space distribution, building shapes, and street arrangements, we selected three representative structures from each LCZ. In the presentation, we will discuss the main difference between the two LCZ types and approach a statement on balancing tree cover and OTC. The findings will help to understand how urban heat stress and thermal comfort are affected by different LCZ layouts and vegetation patterns.