Urban areas represent a complex challenge for the surface energy balance and boundary layer schemes of numerical weather prediction models due to their highly individual nature. Although parameterisation schemes exist for the surface energy balance of urban areas, there is almost no understanding of the importance of the coupling between the surface energy balance and boundary layer. This is important for the evolution of the urban boundary layer and hence also for modelling urban heat islands (which are usually measured via air temperatures).

We have coupled a surface energy balance model for an urban canyon system to a 1-D boundary layer model. The diurnal cycle of this urban model shows strong differences in air temperature, boundary layer height and structure from a simulated rural case. This simple model shows promise in explaining measured intensities of urban heat islands.