Field measurements and modelling of Urban Meteorology in Birmingham, UK

In order to develop dispersion models the parameterisation of urban meteorology must be improved, particularly the diagnosis of stability over a town or city. An increased understanding of this could in turn lead to improved air quality forecasts.

Observations play a large part in developing the understanding and parameterisation of dispersion in the boundary layer, but there is a lack of observational data from UK cities. Field measurements, taken at heights up to 45m, have been carried out at an industrial site in Birmingham. Analysis of the data will be discussed, as well as the practicalities and problems associated with such an urban measurement campaign.

The measurements have been used to analyse a Surface Energy Balance (SEB) canopy model, developed at The Met. Office. However, the model is expected to have limitations as the application of Monin-Obukhov theory is not necessarily appropriate to urban areas.

The model was originally designed for rural areas and run using a vegetation canopy, but this can be altered to a concrete canopy to represent urban areas. The SEB model has been run using both canopy versions. Initial results indicate that modelled radiation and temperature terms show reasonably good agreement with observations, but there are significant problems in predicting heat flux terms and Monin-Obukhov lengths. This indicates that the model handles parameters influenced by the local environment better than those influenced by a much larger area. This is a result of model assumptions of homogeneity which are not appropriate for urban areas.

This work indicates that the SEB model needs considerable development before it can be used for urban applications.