Stuffy rooms are uncomfortable: when it’s winter, the heat is running and the windows are closed, we find it hard to breathe. Letting in some fresh air can make all the difference. The same principle applies to cities, too. The better the air flow, the healthier and more comfortable the climate in our city. Wind is key here. It swirls and dilutes the polluted air and takes it away.
In certain built-up areas, however, near-ground wind speeds are up to 30 percent lower than in the open countryside. As a result, air pollutants cannot be evacuated fully and, in summer, heat islands form. Or the exact opposite might happen, i.e. strong wind speeds can occur next to certain types of buildings and in urban canyons. Dust is then whirled up and irritates our eyes.
In Berlin, (long-term) measurement series are available on horizontal wind conditions recorded by various wind measuring stations. Climate monitoring vehicles were used for a mobile data collection, which enabled us to record relevant urban areas at specific times of day/ night. While top wind speeds are generally reached around lunchtime or in the early afternoon, the lowest wind speeds occur at night. Day and night measurements were therefore analysed separately. This produced two averages for each measuring point, which were assigned to the urban structure types defined in the Environmental Atlas. We were thus able to develop a comprehensive representation in 14 groups.