Evaluation of two simple street canyon carbon monoxide models

Abstract

The main objective of this work was to evaluate and compare two street air pollution models known as STREET model and Nicholson's model. The original versions of the models were modified so as to be able to accommodate the data available. The modified versions of the models were then coded using Java®. The associated computer programs were used with data from the street canyon Jagtvej in Denmark. Data from the models were then compared with measured data. An intercomparison of the two models was also carried out. Scatter plots of modelled against measured CO concentrations yielded a regression coefficient of 0.54 and higher value when considering concentrations not exceeding 3000 µg m-3. The performance of Nicholson's model is inferior with a regression coefficient of 0.17. The time series analysis of the STREET model gave a good accordance between the measured and modelled concentrations, while that for Nicholson's model yielded inferior results. From the analysis of the dependence on traffic passing in the street over a whole day the regression coefficients obtained were 0.76 and 0.71 for the STREET and Nicholson's model respectively. The comparison between diurnal variation of the modelled CO concentration against the actual diurnal variation in CO concentration was well simulated by both models giving two lines following the same trend and two peaks at approximately 0800 and 1700.