Wind and Urban Comfort: What Level of Detail is Required for Wind Data in Outdoor Comfort Assessment?

In the context of global warming, cities are striving to maintain comfortable public spaces. Wind speed significantly affects pedestrian thermal comfort in urban areas, making localized wind data crucial for urban planners. However, obtaining accurate wind data or calculating it using numerical simulation tools remains complex, limiting their systematic use. This study aims to quantify the impact of wind data accuracy on pedestrian comfort assessments.

The "Ydeal" urban block, located in the Confluence neighbourhood of Lyon, France, serves as a case study. Numerical simulations are conducted using SOLENE-microclimat to compute microclimatic variable fields based on different sources of wind velocity data.

Four types of wind data are considered as inputs:

    1. Continuous wind data from the Bron airport meteorological station, located 9 km southeast of the study area.

    2. Wind data from a weather station located 100 meters north of the urban block.

    3. Wind data from a rooftop weather station on the central building within the urban block.

    4. Wind velocity fields derived from numerical simulations at pedestrian scale.

The first three inputs (1, 2, and 3) provide a uniform wind distribution across the urban block but with different intensities. In contrast, the fourth input (4) offers a heterogeneous wind distribution. In all cases, wind speed intensity varies on an hourly basis.

The results from each method will be compared with one another. Subsequently, each dataset will be used as input for pedestrian thermal comfort modelling, using the Universal Thermal Climate Index (UTCI). The study evaluates how each approach affects UTCI outcomes. Finally, based on the complexity of implementation, the most suitable methodology for urban planning applications is recommended.