Modeling the Contribution of the Brussels Heat Island to a Long Temperature Time Series

Abstract

A mesoscale meteorological model containing a detailed land surface model is used to assess the contribution of urban heating to the temperature record of the national recording station of Belgium in Uccle, near Brussels. The Advanced Regional Prediction System (ARPS) was applied over a domain of 60 km ? 60 km with a horizontal resolution of 1 km. Four meteorological episodes were selected, and, for each of these, the model was integrated using two different land cover situations. The first consisted of a detailed reconstruction of the early nineteenth-century setting of Brussels and its wide surroundings, while the second corresponded to the present-day land cover. Since the nineteenth century, when the recording station of Uccle was established, a major land cover change from an agricultural area to a built surface has taken place. The temperature difference between the simulations at the site of Uccle was assumed to represent the urban effect on the site since the beginning of recording. The urban heat island (UHI) of Brussels was found to have a significant impact on the temperature record in Uccle. The urban?rural temperature difference was found to build up during the evening, gradually decreasing during the night and becoming zero during the day. By analyzing the surface energy balance it was revealed that the UHI is mainly caused by a greater storage of energy in the urban fabric during the day and a release of this heat in the evening. The UHI had a significant average impact on the Uccle temperature record during two of the four selected weather situations. The effect amounted to 0.77°C in a cloudy weather situation with westerly winds and to 1.13°C in a clear and calm weather situation.