METEOROLOGICAL PRE-PROCESSING AND ATMOSPHERIC DISPERSION MODELLING OF URBAN AIR QUALITY AND APPLICATIONS IN THE HELSINKI METROPOLITAN AREA

pre-processing and atmospheric dispersion modelling of urban air quality and applications in the Helsinki metropolitan area This theses describes the boundary-layer parameterisation model, which is applied as a meteorological pre-processor by Finnish regulatory dispersion models. The parameterisation scheme is based on the energy-flux method, which evaluates the turbulent heat and momentum fluxes in the boundary layer. A comparison of the model predictions with those of the corresponding scheme of Berkowicz and Prahm, using the same synoptic input data is presented. The comparison shows the basic physical differences between these two models. Some numerical results calculated by these two pre-processors differ substantially, while the results for net radiation are statistically nearly identical. Meteorological profile data from Finnish sounding stations is compiled and the inversions (the temperature of the atmosphere increases with altitude) are classified according to the total depth of the inversion and the stability of the boundary layer, which was estimated directly from the temperature gradient in the layer from the ground up to 100 meters. The persistence of the inversions and the influence of cloudiness and wind speed on the temperature gradient are also addressed. The specific problems of an urban area is tackled, usin