High spatio-temporal and continuous monitoring of outdoor thermal comfort in urban areas: A generic and modular sensor network and outreach platform

Abstract

This study presents an operational citywide monitoring network designed to measure meteorological and human biometeorological variables at a high spatio-temporal resolution. The network is based on an in-house developed, generic data logging and monitoring platform, with 13 stations strategically placed at the pedestrian level on public street lights within the urban canopy layer of Freiburg im Breisgau, Germany. Over the first year of deployment (August 2022 to August 2023), the stations continuously collected high-resolution data (30 s intervals) with a minimal data loss rate of 2% for half of the stations which underscores the robustness of the network. The collected data includes Black Globe temperature, used to calculate the Physiologically Equivalent Temperature (PET) and other thermal comfort indices such as Tropical Night. A case study focused on a July 2023 heatwave showed that residential mid- to low-density areas experienced 16.5 to 18.7 h of extreme heat stress, while inner-city sites recorded the highest number of tropical nights ($T_{a,min\left(1h\right)}$ $\ge$ 20 °C), with 5 to 6 nights, compared to 3 in outer areas. The findings demonstrate significant spatial variability in thermal stress across urban microclimates, particularly during extreme weather events. To address the gap in real-time data dissemination and science communication, we developed the uniWeather outreach platform and app, providing end-users and the public with free access to real-time data, following FAIR principles. This continuous data set is invaluable for urban climate modelers, offering real-time monitoring and insights into localized thermal stress, and can inform urban heat mitigation strategies and adaptation planning for policymakers and city planners.