An examination of relationships between urban and rural micrometeorology using semi-empirical and comprehensive models

An air mass is modified as it is transported from a rural area to an urban area. Therefore, turbulence parameters relevant to air pollution dispersion calculations are also modified. In this paper, we use 1D and 2D semi-empirical methods (including similarity theory) to examine relationships between urban and rural micrometeorology, with a particular emphasis on the application of these relationships in air pollution dispersion calculations for regulatory use. For this purpose high quality data from the Basel Urban Boundary Layer Experiment (BUBBLE), conducted during June¬ – July 2002 in an urban environment in Switzerland, are analyzed. As part of the analysis, we investigate whether it is possible to estimate micrometeorological variables at an urban site in terms of those measured at a rural site, given the surface characteristics of the former. This is important because rural data are normally available (e.g. at an airport) whereas urban data, which are most relevant to pollution predictions in an urban environment, are usually not. Further, we apply a 3D prognostic model, CSIRO's TAPM, to the BUBBLE experimental area in order to characterize the rural and urban flow fields and evaluate the above semi-empirical relationships. TAPM is run with a fine spatial resolution (0.5 km) with multiple nesting, and is able to simulate local effects on the surface flow field. Selected results from the above analysis will be presented.