Cities are characterized by densely built-up areas and surface sealing. This leads to higher air temperatures and reduced wind speeds. Buildings and streets store the energy of solar radiation during the day and release this energy in form of heat at night. Wind speed, and thus ventilation of the city, is often reduced by buildings. Vegetation such as urban trees or green spaces, which provide shade and cooling by evaporation, can be rare.
To better understand and monitor temperature patterns and precipitation amounts in cities, we have installed 180 stations in the city center of the Swiss City Basel and it's surroundings. Based on those measurements, urban heat islands are detected and visualized on a map:
The map shows high temperatures (in red) around the city center of Basel and cooler temperatures in the rural areas. There are, however, very local heat islands. This urban heat island effect is a typical phenomenon of the climate of a city and is characterized by an air temperature difference between the heat-exposed city center and the cooler rural areas. The largest air temperature difference typically occurs during night and can be (depending on the city) up to 10 °C (degrees Celsius).
The starting point of the current high temperatures is a pressure ridge over Western Europe which transports warm air from Africa towards the Iberian Peninsula, and leads to temperatures of up to 42ºC in the region. in the course of the week, this ridge moves in the direction of France and Germany, while weakening, but can still lead to temperatures of up to 35 ºC there. You can check out the heat wave on our maximum temperature map.
To better detect city-specific climate patterns, our city climate monitoring system offers the following features:
- Mapping of local climate zones as shown on the map
- Small-scale city climate model with a horizontal resolution of 10m
- Decision support for mitigation strategies
- Measuring effects of mitigation activities
At the moment, we are operating such station networks in Basel and Zurich in Switzerland. Measurements are shown on our city climate page in real-time as well as for the past 3 days. You can click on each weather station to see measurements data and the station itself.
Since the heat wave is predicted to move to Switzerland, too, temperatures are likely to increase in the city and may hit 40°C in some urban heat islands. If you send us a screenshot of one of our city climate stations in Basel or Zurich with measurements exceeding 40°C, you will get a free point+ subscription for 3 months.
