A comparison of model performance between ENVI-met and Austal2000 for particulate matter

Abstract

This study evaluates the performance of the German dispersion model Austal2000 according to the technical instructions on air quality control (TA Luft), a Lagrangian model, in four real-world particulate matter test cases against ENVI-met, a microclimate model featuring a pollutant dispersion module that bases on the Eularian approach. The four test cases include different traffic induced area sources of PM10, complex terrain with varying ground surfaces and different urban obstacles i.e. buildings. A comparison is made between the calculated concentrations of both models. Furthermore, predictions are compared with field data. Particle measurements are conducted with an optical particle counter. For evaluation, quantile-quantile plots as well as further performance measures i.e. the fractional bias and the robust highest concentration that focuses on the important high-end concentrations are applied. Both models underpredicted observed PM(0.25;10) concentrations for all test cases. All datasets show that predictions of both simulation tools were closer to field observations in the high-end concentration range. Model calculation results show mostly better agreement to observations under neutral stability classes of the atmosphere. With the exception of ENVI-met in one test case predictions of simulation runs of both models lead to results closer to observations when initiated with local meteorological measurement data, where wind speed as one of the key drivers of dispersion models was lower. In almost all of the test cases, Austal2000's predictions were closer to the field observations than those of ENVI-met. The latter model undercut predicted PM10 concentrations of Austal2000 by the factor of around two. This evaluation indicates that Austal2000 is the stronger model compared with ENVI-met considering the distribution of PM10 in complex and urban terrain.