Heat-walk: How do biometeorological indices modeled by modern numerical tools correspond with real human thermal sensation?

Manifestations of climate change and the urban heat island effect increase urban residents' exposure to heat stress, further impacting their physical and mental well-being. These challenges highlight the need for more effective, adaptable, and holistic mitigation and adaptation strategies to reduce heat stress and enhance the urban thermal environment. In this contribution, we introduce outcomes combining two methods: i) high-fidelity simulation of the urban environment with a realistic spatial and temporal setup (1 min and 1 m); ii) thermal walks (aka ‘heat-walk’) conducted during hot summer days in Prague, a central European city. The combination of accurate fine-scale model simulations with a real-time, on-site, human-oriented approach provides comprehensive information about the realistic human thermal environment at the pedestrian level and reveals causes of thermal discomfort. Both methods precisely and consistently identify hotspots that should be improved in terms of thermal comfort. Vulnerable areas are typically open spaces and arterial streets with a lack of greenery and a high proportion of impervious surfaces, unshaded northern parts of streets (typically E-W oriented), or parts of boulevards with inappropriate tree spacing. The results also emphasize the significance of accurately positioned blue-green infrastructure in mitigating urban heat effects. Although both approaches are demanding in terms of obtaining input data, the results are unique regarding time and spatial scale. The findings of these studies can enhance our understanding of the complex spatiotemporal dynamics of human thermal comfort in urban environments, aiding in effective urban planning and urban heat mitigation.