An overview of four use cases from a dense urban measurement network in Basel, Switzerland: Quality of the measurements, temperature and precipitation variability, and mitigation of urban heat island mitigation strategies.

Nowadays, cities worldwide cope with challenges such as air pollution, extreme air temperatures, and heavy precipitation. In the future, these problems will occur more often due to climate change. This trend will result in an unknown amount of economic damage and endanger the life and health of the cities’ populations. Therefore, heatwave management monitoring tool is required to monitor the climate in the city. 

In 2019, more than 200 low-cost IoT temperature and precipitation sensors have been installed in the Swiss city of Basel. In this study we present four use cases from the "Basel Living Lab" based on the measurement network, which are relevant for city planners, decision makers in cities and the citizens itself:  

1. Quality of the measurements

2. Temperature variability in the city 

3. Precipitation variability in the city 

4. Mitigation of urban heat island mitigation strategies 

1. The quality of the low-cost measurement network is estimated by a comparison with official MeteoSwiss stations. Therefore, low-cost sensors have been installed at the same mast as the MeteoSwiss stations as the reference. Reproducibility tests have been conducted, gaps and sensor drifts over the last 4 years have been analyzed and radiation errors have been estimated and corrected. During calm conditions in summer, the low-cost IoT measurements are up to 5 degrees higher than the reference measurements caused by heat accumulation errors which can be corrected satisfactorily with the radiation correction.  

2. The temperature variability in the city and rural surroundings show differences up to 10 degrees during night and calm conditions and on average differences around 3 degrees. The measurement data can be used to force models resolving the urban heat island effect in the city.  

3. The precipitation variability in the city shows differences up to 80 mm/day of precipitation within a few kilometers during heavy thunderstorms. 

4. A small area in Basel, so called “Triangel” was desealed and planted with 18 young trees. Measurements before and after the mitigation phase have been conducted to analyze the effect of the change in the surface conditions. Our results show a decrease in the air temperature of about 0.5 degrees due to the changing surface characteristics, which fits well with scientific studies and model results.  

The four use cases demonstrate some selected advantages of a dense measurement network in an urban environment and build a solid data basis for decision makers in cities mitigating their urban heat island effect.