European researchers study urban heat islands on bikes, from the air and from space

Cordis News: This summer, research teams studied the climate-change-related phenomenon of 'urban heat islands' using bicycle-mounted equipment in the Netherlands and ground-based and airborne technologies over Greece. Both investigations are part of a wider effort to understand, mitigate and adapt to rising temperatures in European cities.

Heat waves strike cities hardest because they are densely laid out and green space tends to be limited. Higher daytime temperatures and reduced night-time cooling in cities compared to the surrounding area are collectively referred to as the 'urban heat island' effect. The elderly are particularly hard hit; during heat waves, urban mortality rates are well above average.

This August, researchers from Wageningen University in the Netherlands loaded two cargo bicycles with measurement equipment and rode them through Rotterdam and Arnhem, participants in the EU Future Cities project. The bikes were able to manoeuvre easily through narrow city streets while the solar-powered equipment remained horizontal (and stable enough to operate). Data was collected at various points during a 24-hour period.

The sensors measured temperature, humidity, wind direction and wind speed, as well as the amount of sunlight and heat-radiation exchange. Measurements were taken once per second, and at fixed intervals in the route photographs were taken from 50 cm above the ground (roughly wheel-hub-high) with a fish-eye lens pointed upwards. This helped to establish how much of the ground was overshadowed by either buildings or greenery.

The findings showed a remarkable 7°C difference between Rotterdam city and the countryside beyond the airport during the night. Remarkably, while the city was 2°C hotter than the airport during the day, one of the city's parks (De Twee Heuvelen) was 2.4°C cooler than the airport in the afternoon - a variance of 4.4°C in the urban area. The 'felt', or perceived, air temperature was 6°C higher in the city than at the airport. The results of the Arnhem study were similar….

A panorama of Arnhem from the cathedral tower, shot by Pior