Thermal comfort through climate walking technique: The experience in Lisbon

Mobile micrometeorological measurements provide insights into how environmental conditions and urban morphology interact with humans, particularly in terms of thermophysiological comfort, thermal sensation, and pleasantness. While other indirect factors may also influence thermal comfort, these are beyond the scope of this study.

A compact mobile weather station equipped with sensors, a data logger, and GPS was developed to collect environmental data required to calculate the Universal Thermal Climate Index (UTCI) for an entire year. During the missions, 292 questionnaires on thermal sensation and pleasantness were also gathered. The study aims to assess how specific weather conditions and urban morphology influence thermophysiological comfort, thermal sensation, and pleasantness. Only the summer results used for the present abstract.

Geospatial analysis revealed that compact urban areas, namely with high urban density (UD) and represented by Local Climate Zones (LCZ) 1, 2, and 3, were associated with higher UTCI values (+-1ºC, per comparison with other urban classes), and 11 identified UTCI hotspots across five study areas. This UD impact on UTCI was particularly evident on avenues (6 hotspots). Surveys indicated lower perceived thermal comfort in compact urban areas.

Average daytime UTCI was 5.5% lower in the city compared to its rural surroundings, with inverse patterns at night (44% higher). Certain weather patterns were found to affect UTCI more significantly, and the western part of the city, near the Atlantic Ocean, exhibited lower UTCI without hotspots. However, this area was perceived as unpleasant due to higher wind speeds. In the easternmost areas by the Tagus estuary, wind direction influenced UTCI more markedly. Areas with greater biomass demonstrated lower UTCI scores.

Modelling showed that strategically planting trees could mitigate and revert a UTCI hotspot situation, as demonstrated for one study area.