Thermal-climatic effects of a fairground event in the local area

Thermal-climatic effects of a fairground event in the local area K. Brandt, Bonn, and W. Kuttler, Duisburg-Essen University, Campus Essen

The micro-scale thermal-climatic effects of a fairground have been examined with the example of an event which takes place annually in the city of Bonn (7.4 ° E; 50.7 ° N; approx. 300,000 inhabitants; State of North Rhine Westphalia, Germany), which is attended by up to 1,500,000 people for five days (12.9.-16.9.2003). The area is 8 hectares in size, is on a flat surface at an altitude of 65 m a. s. l., surrounded by a ridge about 100 m at a distance of 2 km in a southerly direction. The current consumption during the fair for the operation of amusement devices such as roundabouts, helter-skelters and catering institutions amounted to 242,900 kWh according to information from the local utilities supply company (RWE-Net). In the evening hours, 80,000 visitors must be expected. For the duration of the fair, a climate station was installed in the middle of the fair area. It recorded the air temperature and the air humidity at an altitude of 2 m every twenty minutes. In addition, mobile measurements (walks and by car) were held at various times during the event. For comparative measurements, two locations outside the area of the fair were selected, one of them 1 km away in north-east direction at the same altitude, the other 5 km away in south-easterly direction at 90 m a. s. l. Vertical profiles of the near surface atmosphere up to 100 m a. g. l. were recorded with measurement device carriers installed in a big wheel. During calm and cloudless weather conditions on four days of the fair, a mean horizontal temperature difference (Ä t = tmarket – toutside) of 2 K was proven. The highest positive temperature differences of up to 8 K resulted, as expected, in the evening hours between 7 p. m. and 11 p. m. o'clock. The analysis of the vertical temperature distribution of the near surface atmosphere showed that up to an altitude of 50 m a. g. l., the air temperature above the fairground area was 5 K higher during calm and cloudless weather than in overcast and windy weather. The higher evening temperatures are to be regarded as positive for the fair, as they decelerate cooling and thus subject the visitors to a pleasant thermal micro-climate for a long time. During the day, only slight positive temperature differences resulted, 0.5 K in the morning and between 1 K and 2 K in the afternoon. The reason for the considerable horizontal and vertical temperature differences to the environment without influence should be the unusually high artificial energy flux density, amounting to more than 300 W/m² in the evening hours. The area-related evening energy fluss density of the visitors, who numbered up to 80,000, was 200 W/m² – taking a metabolic heat flux density of 200 W/person into account.

Summarizing, it can be stated that this fair event caused a relatively strong, both horizontally and also vertically marked heat island intensity. The remarkable thing is that around 60% of this energy is to be put down to the metabolic heat flux density of the visitors.