Urban heat islands

  • Urban heat islands and their location in cities
  • The usage of heat maps in detecting urban heat islands

The urban heat island effect is a typical phenomenon of the climate in a city, and is characterised by an air temperature difference between the heat-exposed city centre and the cooler surrounding rural areas. The largest air temperature difference typically occurs at night and can reach up to 10 degrees (depending on the city). Many site-specific locations inside the city centre are particularly exposed to heat. These are called hot-spots. These hotspots are typically regions with high construction density, street canyons, and sealed surfaces where heat accumulates easily.

The urban heat island map (above) shows the urban heat island intensity for the city of Zurich (CH) in a horizontal resolution of 10 x 10 m, as an example. Areas in red indicate hotspots, whereas blue areas represent cooler areas.

With the aid of the heat maps, specific local information can be obtained on tropical nights, heat days, heating days, and cooling days. These analyses can be calculated both for the current year, and for the near and distant future using the RCP emission scenarios. The analyses thus constitute an important scientific contribution to the heat management of a city, and provide an important decision support tool for supporting cities in fighting climate change with reliable data.